Knowledge and research data APIs and MCP servers for AI agents
Encyclopedias, academic papers, news, computational knowledge and up-to-date library documentation.
19 knowledge and research data APIs an AI agent can call: auth method and header, official MCP server (6), free tier (19), docs links. Machine-readable JSON included. Agents: fetch catalog/knowledge-research.json instead of parsing this page. Last checked 2026-11-04.
Ratings and usage (★) fetched: .
| Service | What an agent can do | Auth | MCP server | Free tier | Details (with sources) | Notes | Proof (ratings, usage) |
|---|---|---|---|---|---|---|---|
| arXiv API | Search arXiv preprints by keyword, author, category or ID and retrieve metadata, abstracts and PDF links. | noneno auth | community | free, no key | Base URL: http://export.arxiv.org/api/query Free plan: no_key, no card ↗ Rate limits: No more than 1 request every 3 seconds, single connection at a time, across all your machines; max_results slices of 2000, 30000 total ↗ Example call: search preprints by keyword: GET http://export.arxiv.org/api/query?search_query={query}&start=0&max_results={n} ↗ MCP tools: 12: search_papers, get_abstract, download_paper, list_papers, read_paper, get_paper_outline … ↗ | Endpoint: http://export.arxiv.org/api/query, returns Atom XML. Terms of Use allow no more than one request every three seconds over a single connection. For bulk harvesting use OAI-PMH or bulk data instead. | |
| Congress.gov API | Lets an agent look up U.S. bills, amendments, votes, members, committees, nominations and Congressional Record data from the Library of Congress. | API keyapi.data.gov key: query parameter ?api_key=<API_KEY> or header X-Api-Key: <API_KEY> | community | Free: government API, key issued instantly by email; 5,000 requests/hour. | Base URL: https://api.congress.gov/v3 Free plan: 5,000 requests per hour, no card ↗ Rate limits: 5,000 requests per hour ↗ Example call: list bills of a Congress by type: GET https://api.congress.gov/v3/bill/{congress}/{billType}?format=json&api_key={API_KEY} ↗ MCP tools: 11: congressgov_bill_lookup, congressgov_enacted_laws, congressgov_member_lookup, congressgov_committee_lookup, congressgov_roll_votes, congressgov_senate_nominations … ↗ | Official Library of Congress API (v3); usage guide and endpoint docs in github.com/LibraryOfCongress/api.congress.gov. Paginated JSON/XML, max 250 results per page. | |
| Context7 (library docs for agents) | Fetch up-to-date, version-specific library documentation and code examples into a coding agent's context via MCP or REST. | API keyAuthorization: Bearer <ctx7sk_... key> (optional; works at low limits without key) | official | Free: 1,000 API calls per month with a free API key (low limits without key); Pro $10/seat/month | Base URL: https://context7.com/api/ Free plan: 1,000 API calls, per month ↗ Rate limits: Low limits without key; plan-based limits with key; 429 with Retry-After and RateLimit-* headers when exceeded ↗ Example call: fetch up-to-date documentation snippets for a library: GET https://context7.com/api/v2/context?libraryId={libraryId}&query={query} ↗ Unit price: Per API call: Free 1,000 calls/month; Pro $10/seat/month includes 5,000 calls per seat, then $10 per 1,000 calls ($0.01/call) ↗ MCP tools: 2: resolve-library-id, query-docs ↗ | Maintained by Upstash; repo https://github.com/upstash/context7. Local server @upstash/context7-mcp, also a ctx7 CLI and @upstash/context7-sdk. REST base URL: https://context7.com/api/. Exceeding the limit returns 429 with Retry-After/RateLimit-* headers. Paid plans cover teams and private repos. | |
| Court Rules | Lets an agent read U.S. federal and local court rules, judge standing orders, court holidays and filing deadlines, and compute a filing deadline for any federal district. | API keyAPI key from your Court Rules account (sign up at courtrules.app; Developer plan is $0), sent as Authorization: Bearer <COURT_RULES_API_KEY>; the hosted MCP server also accepts OAuth sign-in from the MCP client. | official | free tier: Developer plan at $0/month with full API access, rate limited to 10 requests/minute | Free plan: Developer plan $0/month, full API access, 10 requests/minute ↗ Rate limits: 10 requests per minute on the free Developer plan ↗ | Vendor-hosted MCP server at https://mcp.courtrules.app/mcp takes the same API key in the Authorization: Bearer header; TypeScript and Python SDKs are offered. | — |
| Crossref REST API | Look up and search scholarly metadata such as DOIs, references, authors, funders and licenses across Crossref-registered works. | noneno key; add mailto=<email> param or User-Agent contact for the 'polite pool' | community | free, no key | Base URL: https://api.crossref.org Free plan: no_key, no card ↗ Rate limits: Public pool 5 req/s, concurrency 1; polite pool (mailto) 10 req/s, concurrency 3; Metadata Plus 150 req/s ↗ Example call: search scholarly works metadata: GET https://api.crossref.org/works?query.bibliographic={query}&rows={n}&mailto={email} ↗ MCP tools: 3: search_papers, fetch_paper_details, search_by_topic ↗ | Base URL https://api.crossref.org (/works, /journals, /funders, /members). Rate limits are fixed per pool: public 5 req/s (concurrency 1), polite with mailto 10 req/s (concurrency 3); 429 when exceeded. Metadata Plus is a paid SLA tier (150 req/s). | |
| DC Hub | Lets an agent check where data centers can get grid power, using the Data Center Power Index (DCPI) daily score across 300+ markets, plus grid, interconnection-queue, fiber and site data. | API keyX-API-Key: <DCHUB_API_KEY> header (or Authorization: Bearer <key>) on both the REST API and the MCP server; anonymous calls return previews. A key is issued self-serve with POST https://dchub.cloud/api/v1/keys/claim. | official | free tier: keyless previews; a free self-serve key adds 2 full answers per tool per day, and 50 calls/day once an email is added | Base URL: https://dchub.cloud/api/v1 Free plan: Anonymous previews; free key: 2 full answers per tool per day; with an email: 50 calls/day, no card ↗ Rate limits: Free key: previews plus 2 full answers per tool per day; with an email: 50 calls/day (up to 10 full answers per tool per day); Starter 200/day, Developer ($49) 500/day, Pro ($99) 2,000/day ↗ Example call: get the Data Center Power Index of a market: GET https://dchub.cloud/api/v1/dcpi/scores/{market_slug} ↗ Unit price: Daily call caps, not per-call prices: Developer $49/mo for 500 MCP calls/day, Pro $99/mo for 2,000 calls/day plus site-analysis tools ↗ | Remote Streamable HTTP MCP server at https://dchub.cloud/mcp; works without a key for previews. Keyless REST endpoints include GET /api/v1/stats and /api/v1/markets/list. On the free tier the DCPI endpoint returns only the BUILD/CAUTION/AVOID verdict; the numeric scores (composite, excess power, constraint, months to power) need a paid plan. | — |
| GDELT API | Full-text search global news in about 65 languages and analyze coverage volume, tone and geography in near real time. | noneno auth | community | free, no key | Base URL: https://api.gdeltproject.org/api/v2/doc/doc Free plan: no_key, no card ↗ Example call: search recent global news articles: GET https://api.gdeltproject.org/api/v2/doc/doc?query={query}&mode=artlist&maxrecords={n}&format=json ↗ MCP tools: 9: gdelt_search_articles, gdelt_get_coverage_timeline, gdelt_get_tone_distribution, gdelt_get_coverage_breakdown, gdelt_search_tv, gdelt_get_tv_clips … ↗ | DOC 2.0 API: https://api.gdeltproject.org/api/v2/doc/doc. Covers a rolling window of about 3 months, max 250 records per query. GEO 2.0 and TV APIs also exist. Full historical Events/GKG data available via Google BigQuery (needs a billed Google Cloud account). | |
| Gitingest API | Lets an agent turn any public Git repository into a single text digest (summary, directory tree and file contents) sized for an LLM prompt. | noneNo key for public repos: GET https://gitingest.com/api/<owner>/<repo>; optional GitHub token for private repos via the 'token' parameter | community | No key needed: free public service; hosted API limited to 10 requests/minute per endpoint (the web UI also has rate limiting and CAPTCHA protection). | Base URL: https://gitingest.com/api Free plan: no_key, no card ↗ Rate limits: 10 requests/minute on POST /api/ingest and GET /api/{user}/{repository} (per server limiter) ↗ Example call: turn a public GitHub repo into a text digest: GET https://gitingest.com/api/{user}/{repository} ↗ MCP tools: 1: ingest_git ↗ | GET /api/{user}/{repo} or POST /api/ingest (include/exclude patterns); digest returned inline (summary, tree, content) plus a download URL. For heavy use the vendor recommends the open-source CLI (pip install gitingest). | |
| Hacker News API | Read Hacker News stories, comments, jobs, polls, user profiles and front-page rankings as real-time JSON. | noneno auth | community | free, no key | Base URL: https://hacker-news.firebaseio.com/v0/ Free plan: no_key, no card ↗ Rate limits: There is currently no rate limit ↗ Example call: get a story or comment by id: GET https://hacker-news.firebaseio.com/v0/item/{id}.json ↗ MCP tools: 1: get_stories ↗ | Base URL https://hacker-news.firebaseio.com/v0/. Read-only, no documented rate limit. No full-text search; use the separate Algolia HN Search API for that. | |
| Internet Archive Open Library API | Lets an agent search books, authors and subjects, fetch work/edition data by ISBN or OLID, search inside book texts and get cover images. | noneNo key; send a User-Agent header with app name and contact email, e.g. 'User-Agent: MyApp (me@example.org)' | community | No key; free and open: 1 request/second anonymous, 3 requests/second with an identifying User-Agent. | Base URL: https://openlibrary.org Free plan: no_key, no card ↗ Rate limits: 1 request/second unidentified; 3 requests/second with User-Agent naming app and contact; no bulk download via API ↗ Example call: search books: GET https://openlibrary.org/search.json?q={query} ↗ MCP tools: 7: search_books, get_book_by_title, get_authors_by_name, get_author_info, get_author_photo, get_book_cover … ↗ | Bulk scraping discouraged; use the monthly data dumps for large jobs. Reading-log/list write endpoints need an Open Library login. | |
| New York Times APIs | Lets an agent search NYT articles back to 1851, read top stories, most-popular lists, the Times Wire feed and bestseller lists. | API keyQuery parameter ?api-key=<API_KEY> (create an app at developer.nytimes.com and enable the APIs you need) | community | Free: all public APIs are free; 500 requests/day and 5 requests/minute per API. | Base URL: https://api.nytimes.com/svc Free plan: 500 requests per API, per day, no card ↗ Rate limits: Two limits per API: 500 requests/day and 5 requests/minute; sleep 12 s between calls ↗ Data policy: Non-commercial use only; terms forbid using the APIs or content to develop a software product or train an ML/AI system ↗ Example call: search articles: GET https://api.nytimes.com/svc/search/v2/articlesearch.json?q={query}&api-key={API_KEY} ↗ MCP tools: 5: search_articles, get_latest_news, get_most_popular, get_archive, get_bestseller_list ↗ | Returns metadata/abstracts and links, not full article text. Exceeding limits returns HTTP 429; wait ~12 s between calls. Non-commercial use only; terms forbid using the APIs to develop a software product or train an ML/AI system. | |
| NewsAPI | Search and retrieve current and historical news articles and top headlines from thousands of sources worldwide. | API keyX-Api-Key: <key> header or apiKey=<key> query param | community | free Developer plan: 100 req/day, dev/test only, 24h article delay | Base URL: https://newsapi.org/v2 Free plan: 100 requests, per day, no card ↗ Rate limits: Developer plan 100 requests/day, 24h article delay, dev/test only; Business $449/mo with 250,000 requests/month ↗ Example call: search news articles: GET https://newsapi.org/v2/everything?q={query} ↗ Unit price: Extra requests beyond plan: $0.0018 per request on Business ($449/mo incl. 250,000), $0.0009 on Advanced ($1,749/mo incl. 2M); free Developer plan has no overage ↗ MCP tools: 2: search_articles, get_top_headlines ↗ | Free plan is barred from staging/production, including internal use; CORS allowed from localhost only. Production use needs the Business plan ($449/mo, 250k req/mo). Endpoints: /v2/everything, /v2/top-headlines. | |
| OpenAlex API | Query an open catalog of scholarly works, authors, institutions, sources and topics, including citation data, via REST. | API keyapi_key=<key> query param (optional; basic use works without key) | community | free: $1 of API usage/day without payment method; free key raises daily budget 10x | Base URL: https://api.openalex.org Free plan: $1 of API usage (10x with free API key), per day, no card ↗ Rate limits: Cost-based daily budget ($1/day free, resets midnight UTC); each response reports cost_usd; prepaid top-ups in $1 increments ↗ Data policy: Data released under CC0 ↗ Example call: search scholarly works: GET https://api.openalex.org/works?search={query} ↗ Unit price: search: $1 per 1,000 calls; list+filter: $0.10 per 1,000; single entity: free; content download: $10 per 1,000 (after $1/day free usage) ↗ MCP tools: 5: list_categories, fetch_latest, fetch_top_cited, search_papers, fetch_content ↗ | Base URL https://api.openalex.org. docs.openalex.org redirects to help.openalex.org. Free daily budget resets at midnight UTC; then pay-as-you-go in prepaid $1 increments. Member plans from $5,000/yr. Data is CC0. Listed MCP is a community multi-source papers server (arXiv, OpenAlex, PMC and more). | |
| PubMed E-utilities (NCBI) | Search, fetch, summarize and cross-link biomedical literature records from PubMed, PMC and other Entrez databases. | noneoptional api_key=<NCBI key> query param; tool and email params recommended | community | free; 3 req/s without key, 10 req/s with free NCBI API key | Base URL: https://eutils.ncbi.nlm.nih.gov/entrez/eutils/ Free plan: no_key, no card ↗ Rate limits: 3 requests/second per IP without key; 10 requests/second with free API key (one key per NCBI account) ↗ Example call: search PubMed for article IDs (ESearch): GET https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=pubmed&term={query}&retmode=json ↗ MCP tools: 5: search_papers, search_pubmed, search_pmc, search_europe_pmc, download_with_fallback ↗ | Base URL https://eutils.ncbi.nlm.nih.gov/entrez/eutils/ (esearch, efetch, esummary, elink). Free API key from NCBI account settings. Run heavy jobs off-peak. | |
| Semantic Scholar API | Search papers, authors and citation graphs, and get paper recommendations from Semantic Scholar's academic corpus. | API keyx-api-key: <key> (optional; unauthenticated access allowed) | community | free; no key (shared, throttled pool) or free API key on request | Base URL: https://api.semanticscholar.org/graph/v1 Free plan: no_key, no card ↗ Rate limits: Unauthenticated: 1000 req/s shared among all users, may be throttled; with key: 1 req/s on all endpoints to start ↗ Example call: search papers by relevance: GET https://api.semanticscholar.org/graph/v1/paper/search?query={query}&fields={fields} ↗ MCP tools: 16: paper_relevance_search, paper_bulk_search, paper_title_search, paper_details, paper_batch_details, paper_authors … ↗ | Without a key, all users share a pool of 1000 req/s that can be throttled under load. A key starts at 1 req/s dedicated; requested via web form, arrives by email (not instant). Three APIs: Academic Graph, Recommendations, Datasets. | |
| SemanticHub | Lets an agent set up monitoring of news sources, read clustered articles and generated texts, and manage goals and workflows in SemanticHub. | API key / OAuthPersonal API token (starts with sh_) from Account profile > API tokens at semantichub.app, sent as Authorization: Bearer sh_<TOKEN>; the remote MCP server also supports OAuth sign-in from the MCP client, and the token scope (read or read+write) is enforced there. | official | free forever, no card: 1 goal, 100 sources to watch, 5 workflow nodes, articles kept 7 days; paid plans from $29/month | Free plan: 1 goal, 100 sources to watch, 5 workflow nodes, articles kept up to 7 days, no card ↗ MCP tools: 6: semantichub_whoami, semantichub_api_search, semantichub_api_details, semantichub_api_read, semantichub_api_write, semantichub_search_articles ↗ | The full OpenAPI schema is not public; the supported integration surface is the MCP server (token scope read or read+write is enforced there). A new goal is created as a draft and collects nothing until it is resumed. | — |
| Wikidata | Query the Wikidata knowledge graph of entities, facts and relations via SPARQL, the REST API or MCP. | noneno auth for reads (descriptive User-Agent required); OAuth2 Bearer only for edits | official | free, no key | Base URL: https://query.wikidata.org/sparql Free plan: no_key, no card ↗ Rate limits: Wikimedia limits: 10 req/min IP-only, 200 req/min with proper User-Agent; back off on 429 and honor Retry-After ↗ Example call: run a SPARQL query: GET https://query.wikidata.org/sparql?query={sparql} ↗ MCP tools: 6: search_items, search_properties, get_statements, get_statement_values, get_instance_and_subclass_hierarchy, execute_sparql ↗ | Official MCP comes from Wikimedia Deutschland (github.com/wmde/WikidataMCP). SPARQL endpoint: https://query.wikidata.org/sparql, query timeout ~60s. REST API at /w/rest.php/wikibase/v1. Wikimedia rate limits and User-Agent policy apply. Added because it's a widely-used structured-knowledge source missing from the candidate list. | |
| Wikipedia / Wikimedia API | Search, read and summarize Wikipedia and other Wikimedia content and metadata via REST and Action APIs. | noneReads need no key but require a descriptive User-Agent header with contact info. Optional OAuth2 via Authorization: Bearer <access token> raises rate limits. | community | free, no key (rate-limited) | Base URL: https://en.wikipedia.org/w/api.php Free plan: no_key, no card ↗ Rate limits: 10 req/min IP-only; 200 req/min with User-Agent (unauthenticated or new users); 2000 req/min established editors; max 3 concurrent ↗ Data policy: Text available under CC BY-SA; additional terms may apply ↗ Example call: full-text search Wikipedia articles: GET https://en.wikipedia.org/w/api.php?action=query&list=search&srsearch={query}&format=json ↗ MCP tools: 9: search_wikipedia, get_article, get_summary, get_sections, get_links, get_coordinates … ↗ | The old API Portal at api.wikimedia.org now 301-redirects to mediawiki.org/wiki/Wikimedia_APIs. Documented limits: 10 req/min for requests identified only by IP, 200 req/min for unauthenticated requests with a proper User-Agent, 2000 req/min for established editors. Main endpoints are the per-wiki MediaWiki Action API (/w/api.php) and REST APIs. | |
| Wolfram|Alpha API | Get computed answers, structured data and step-by-step results for math, science and factual queries. | API keyappid=<AppID> query param or Authorization: Bearer <AppID> | official | Free: non-commercial developer AppID with up to 2,000 calls/month; paid for commercial use | Base URL: https://www.wolframalpha.com/api/v1/llm-api Free plan: 2,000 non-commercial API calls, per month ↗ Example call: get a computed answer for a natural-language query (LLM API): GET https://www.wolframalpha.com/api/v1/llm-api?input={query}&appid={APPID} ↗ MCP tools: 3: WolframAlpha, WolframLanguageEvaluator, WolframContext ↗ | LLM API https://www.wolframalpha.com/api/v1/llm-api is built for agents (maxchars, default 6800); get an AppID in the Developer Portal; commercial use needs a paid license. Official MCP: free, no auth at agenttools.wolfram.com/mcp; paid services.wolfram.com/api/mcp (Bearer). |
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