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

Annotations already cover read-only, idempotent, and non-destructive behavior. The description adds valuable behavioral context beyond that: it states the return payload includes claims and sources, and it discloses the behavior for unknown ids (not a dead end, with retry suggestions from the answer). This gives the agent important expectations not captured by 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 two sentences with the primary action and return content front-loaded, followed by usage timing and error behavior. Every sentence carries distinct, necessary information with no redundancy or 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?

With only one parameter, full schema coverage, an output schema present, and annotations covering the safety profile, the description supplies all essential context: what the tool returns, when to invoke it, and how to handle unknown ids. Nothing an agent needs to call it correctly 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 schema description for 'id' has 100% coverage and already explains the id's provenance and format ('as returned by search, answer, get_topic or get_related — the last segment of its canonical URL'). The description reinforces that the id comes from search, answer, or get_topic, but adds no new meaning beyond the schema, so the baseline of 3 is appropriate.

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 uses a specific verb ('Fetch') and a specific resource ('one knowledge object by id'), and further details that the result includes claims and the sources each claim cites. This clearly differentiates it from sibling tools like get_topic or get_sources, which likely fetch different resources or just sources.

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 explicitly states when to use the tool: 'Use this once search, answer or get_topic has given you an id.' It also provides error-recovery guidance for unknown ids, explaining that the answer names near-miss ids to retry. This is an explicit when-to-use instruction that leaves little to inference.

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