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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and non-destructive behavior, so the safety profile is covered. The description adds genuinely non-covered context: missing text is omitted rather than filled in (important for an agent interpreting sparse results) and that output is not legal advice. It does not mention rate limits, auth, or failure behavior for an invalid number.

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?

Three short sentences, front-loaded with the action and returned fields, then the omission caveat and disclaimer. No filler or repetition; every sentence carries 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?

With no output schema, the description usefully enumerates the returned fields, and the single required parameter is fully specified in the schema. It is nearly complete; only error/invalid-number behavior is unspecified, a minor gap for a simple single-parameter lookup.

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 description coverage is 100% and the patentNumber field already documents accepted formats ('US10000000 or 10000000') with length bounds. The description adds only that the target is a US patent, which is already implied by the schema example, so it does not go beyond the schema. Baseline 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?

Specific verb ('Fetch') and resource ('one US patent') plus an enumeration of what is returned (title, abstract, claims, status, family, citations) and the source (USPTO). The singular 'one US patent' implicitly contrasts with the search_* siblings, but no sibling is named explicitly, so differentiation is left to inference.

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?

Usage is implied: this is the lookup-by-identifier tool, so an agent infers it is used when it already has a patent number, versus the search siblings that discover them. There is no explicit when-to-use, when-not-to-use, or named alternative, and 'Not legal advice' is a disclaimer rather than routing guidance.

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