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MCP Tool Specificity

Architect's Playbook Patterns

Definition

The practice of splitting a broad, overloaded custom tool into several highly granular, single-purpose MCP tools so the agent reaches for them instead of defaulting to built-in text tools like Grep.

Key points

  • The trap: Providing a broad custom tool (analyze_dependencies) alongside built-in tools like Grep — the agent defaults to Grep.
  • Anti-pattern — Monolithic Tool: Agent uses built-in Grep to search imports instead of {name: analyze_dependencies}.
  • Architect's pattern — Granular Tools: Agent uses custom tools list_imports, resolve_transitive_deps, detect_circular_deps.
  • The fixes: Split broad tools into highly granular, single-purpose tools; enhance MCP tool descriptions to explicitly detail capabilities, expected outputs, and when to prefer them over text manipulation. Applies similarly to adopting custom refactoring tools over standard Bash/sed.

Why it matters for the exam

  • This is the Developer Productivity × Accuracy cell in the Reference Matrix ("Granular MCP Tools").
  • Tests the diagnosis (agent ignores a broad tool for Grep) and the two-part fix (granularity + better descriptions).

Common gotchas

  • A single overloaded tool is the anti-pattern, not the fix.
  • Good descriptions matter as much as granularity — the tool must say when to prefer it over text manipulation, or the agent still defaults to Grep/Bash/sed.

See also

Sources

Referenced by