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

With no annotations, the description fully discloses behavior: read-only diagnostic, no arguments, reports specific metrics. It covers what the tool returns and implies it has no side effects.

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?

Two sentences: first states purpose, second lists details and usage hint. Every word earns its place, no filler.

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?

With an output schema available, the description does not need to detail return values, but it already does. It covers purpose, usage, behavior, and is self-contained for a zero-parameter diagnostic tool.

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 coverage is 100% (no parameters). Baseline for 0 params is 4. The description adds that it takes no arguments, which is already in the schema, but does not provide additional parameter-level meaning beyond that.

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 reports cache health, token savings, and runtime diagnostics. It lists specific metrics (storage occupancy, hit rates, call counts, memory) and distinguishes itself from siblings by noting it is not for routine read/edit loops.

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?

Explicitly states 'Use it to measure or debug — not as a routine step in read/edit loops,' providing clear when-to-use and when-not-to-use guidance. No alternative tools are named, but the context of siblings (all file operations) makes the diagnostic role obvious.

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