Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With annotations already declaring readOnlyHint=true and idempotentHint=true, the description further enhances transparency by explaining the error behavior: 'this tool never raises a protocol error — it returns {"error": ...}'. It also explicitly states that retrying is safe: 'after correcting the input it is always safe to retry'. No contradictions with annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is very efficient. It starts with a clear single-purpose statement, then lists metrics. Uses whitespace effectively 'FREE' to highlight key aspect. The multi-line structure is readable. Every sentence is necessary, and the example input/output clarifies the tool's behavior without extra fluff.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool has 2 parameters (1 required), 100% schema coverage, and an output schema, the description fully covers the usage. The description explains the output structure ('functions, detail array with name/start/lines/branches/max_depth, flags, note'). It also explains the error case behavior. Nothing is missing for this tool's complexity level.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the baseline is 3. The description adds context about the `code` parameter format ('Full source text to analyze, pasted as a single string.') but does not add significant meaning beyond the schema. The language parameter is also described adequately. No deduction needed as schema fully covers it.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose: 'Report structural complexity of a source file, function by function.' It uses specific verbs like 'Report' and identifies the resource as a source file's complexity. It also distinguishes itself from siblings like 'security_deep_dive' by noting it's for structure, not vulnerabilities.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides explicit guidance on when to use this tool: 'Use when structure rather than correctness is the question.' It also clearly states when not to use it: 'Not for vulnerabilities (security_deep_dive).' This directly addresses when-to-use and when-not-to-use, making it a 5.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.