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

With annotations already covering readOnly/idempotent/destructive, the description goes further: it discloses the ownership scoping rule ('only generations linked to your account'), the 404 and 403 failure modes, and the required scope/API key format. This is exactly the behavioral context annotations cannot express.

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?

Dense but front-loaded with the return shape before the operational caveats. Slightly redundant with 'Read-only operation,' which merely restates the readOnlyHint annotation, but overall every other sentence earns its place.

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?

In the absence of an output schema, the description fully documents the return structure (generationId, audioUrl, duration, wordTimings and their sub-fields) and covers auth and error semantics. Nothing an agent needs to invoke and interpret this call 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?

Schema coverage is 100% and the single generationId parameter is fully documented in the schema, so the description need not repeat it. Baseline 3 applies; the description adds no format or syntax detail beyond the schema.

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?

Opens with a specific verb+resource ('Fetches narrador X generation audio and metadata') and immediately enumerates the returned fields. An agent can distinguish this from the sibling generate_x_audio without opening a schema.

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 routes usage: 'retrieve a generation if generate_x_audio was called earlier or to re-fetch audio,' tying it to a named sibling tool. It gives clear context but no explicit when-not-to-use case or alternative retriever.

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