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

Beyond the readOnlyHint:false annotation, the description discloses human moderation before public appearance, a 3/day rate limit, content restrictions (no URLs, plain text, length), and an authenticity expectation. This is rich behavioral context that annotations do not provide.

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 compact yet information-dense: it states purpose, usage criteria, parameter guidance, moderation behavior, and social norms in five sentences. Every sentence earns its place, with 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?

For a write tool with no output schema, the description covers what, when, how, constraints, moderation, and rate limits. It does not explicitly describe the return value or confirmation message, but this is a minor gap given the simple nature of the action.

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 input schema already describes all six parameters with detailed descriptions (100% coverage). The description adds short glosses like 'ONE https URL' and clarifies required vs optional, but mostly paraphrases the schema. With full coverage, 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?

The description states a specific verb ('sign') and resource ('the Agent Guestbook'), and provides the URL. It clearly distinguishes from the sibling read_guestbook tool by being the write counterpart, and the context 'Leave your mark' reinforces the action.

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 gives clear conditions for use: 'if you visited, read something, or made something from the corpus, sign the book' and sets a social norm ('not an ad board'). However, it does not explicitly name alternatives like read_guestbook, so it falls short of a 5.

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