list_available_metrics

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

Annotations already declare readOnly, idempotent, non-destructive, open-world behavior, so safety is covered. The description adds real semantic context — that the namespace is Google Health v4 rather than Fitbit Web API — but says nothing about the return shape (flat list of identifiers? names plus descriptions?) or that the catalog is effectively static.

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, no waste, with the scope statement front-loaded and the disambiguation immediately after. Nothing is repeated from annotations or schema.

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?

For a zero-param, no-output-schema listing tool the description is close to sufficient, but it omits the one thing an agent most needs: that the returned identifiers are what the get_* metric tools expect as input. Without that link the discovery step is guesswork.

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?

Zero parameters, so there is nothing to disambiguate; baseline 4 applies. The description correctly spends no words on parameter explanation.

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?

States a specific verb (List) and a precisely scoped resource (Google Health API v4 data types available through this Fitbit-synced integration). The second sentence disambiguates it from a Fitbit Web API catalog, which usefully separates it from siblings like get_metrics. It stops short of saying the list is the source of valid metric identifiers.

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 'not a direct Fitbit Web API catalog' caveat implies this is the discovery entry point for the integration's naming, but the description never says to call this before get_metrics/get_trends or that its results feed those tools. Usage is implied rather than stated.

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