repo_cache_stats

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds meaningful context beyond those: the data is in-memory, runtime diagnostics, and has zero side effects, which clarifies that the values are ephemeral and the call cannot influence server state.

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 front-loaded with the action and metric list, and each remaining sentence adds distinct value: side-effect declaration, when to use, when not to use, and expected output. It is concise enough for a zero-parameter tool while providing genuinely useful routing information.

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 zero parameters, no output schema, and rich annotations, the description covers everything an agent needs: what the tool does, which metrics it returns, the side-effect profile, and explicit alternatives. The output format is also stated ('JSON object with cache metrics'), so no critical information is missing.

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?

The tool has zero parameters, and the schema description coverage is effectively 100% (empty schema), so there are no parameter semantics for the description to add. The baseline for zero-parameter tools is 4, and the description appropriately emphasizes that the tool is a straightforward read of counters without needing inputs.

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 opens with a specific verb and resource: 'Retrieve runtime diagnostic counters for the tool result cache' and enumerates the exact metrics returned. It also explicitly contrasts with sibling tools by stating that repo_map and repo_search are for repository contents and structure, making differentiation clear.

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 'When to use' guidance (evaluating cache hit rate or debugging server performance) and explicit 'When NOT to use' guidance with named alternatives (repo_map or repo_search for repository content/code structure). This is the strongest possible usage guidance.

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