docs-lookup

Docs Lookup (with fallback)

When you need authoritative information about an unfamiliar tool / API / error message / library behavior, follow this fallback chain. Each step has explicit success and failure criteria so the agent never silently degrades to guessing.

Step 1: Structured docs MCP   (Context7; or Microsoft Learn for .NET/Azure/Windows/MSVC)
   ↓ (unavailable / no match / wrong content / tool error)
Step 2: WebSearch     (broader web, recent ecosystem changes)
   ↓ (unavailable / no useful results / paywalled)
Step 3: Calibrated uncertainty (tell user what you tried + what's needed)

You do not skip steps. If Step 1 fails, you go to Step 2. If Step 2 fails, you go to Step 3. You do NOT retry Step 1 with the same query hoping for a different answer.

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Step 1: Structured docs MCP — Context7, or a first-party MCP for its ecosystem

When it's the right tool: API references, configuration options, well-known libraries (React, CMake, Clang, etc.), version-specific behavior.

Two-call usage (typical Context7 / Microsoft Docs MCP shapes):

1. resolve-library-id(library_name)            → canonical id, e.g. /llvm/clang
2. get-library-docs(id, topic="<question>")    → structured snippet + citation URL

(Tool names vary by harness: mcp__Context7__*, mcp__plugin_context7_context7__*, mcp__73bcda44-…__query-docs, etc. Use whatever resolves to "Context7" in your tool inventory.)

First-party ecosystem docs MCP — prefer it over Context7 when the topic matches. Context7 is the general default for libraries, but if the question is about a specific vendor ecosystem and that vendor's docs MCP is in your inventory, it is higher-signal (first-party). The prime example: Microsoft Learn (microsoft_docs_search → microsoft_docs_fetch; microsoft_code_sample_search for snippets) for .NET / Azure / Windows / MSVC / Win32 topics — including MSVC compiler errors and Windows-SDK headers in C/C++ work. Same two-call shape (search → fetch) and the same failure-mode handling below; if it is absent or returns nothing useful, fall through to Context7 → WebSearch as normal. (General principle — prefer the first-party MCP for its ecosystem; not a hard dependency.)