AochenShen99 2bbc7879fa
refactor(tool-search): consolidate MCP metadata tag and harden deferred-tool setup (#3370)
Follow-up to #3342 (deferred MCP tool loading). Maintainability cleanup plus
hardening of malformed/empty tool_search queries; no change to the deferral
mechanism or search ranking.

- Add deerflow/tools/mcp_metadata.py as the single source of truth for the
  "deerflow_mcp" tag (MCP_TOOL_METADATA_KEY + tag_mcp_tool + public
  is_mcp_tool). Removes the duplicated magic string and the private,
  cross-module _is_mcp_tool import.
- tool_search.search: never raise on model-generated input. Extract
  _compile_catalog_regex (shared compile-with-literal-fallback); return empty
  for empty/whitespace queries and a bare "+" instead of matching everything
  or raising IndexError.
- DeferredToolSetup: document the empty-vs-populated invariant.
- build_deferred_tool_setup: comment the two distinct empty-return branches.
- _assemble_deferred: add return type, rename local to deferred_setup, build
  the final list with an explicit append.
- Tests: use tag_mcp_tool instead of per-file tag helpers; cover empty and
  bare-"+" queries.
2026-06-05 15:21:41 +08:00
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