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

The description transparently discloses key behaviors: it returns nothing ('nothing is returned to you'), is asynchronously read by a human, is never published, and includes a privacy caution ('do not write anything from the conversation'). No annotations exist, so the description carries this responsibility well.

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 overly poetic and verbose for a simple tool, taking multiple sentences to convey a basic write-only action. It is not front-loaded with clear technical purpose; the key functional details appear later. A more direct and concise description would be preferable for an MCP tool.

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 simple tool with one parameter and no output, the description covers the essential context: what it does, the return behavior, the human-read nature, and a privacy note. It is sufficiently complete for the tool's simplicity.

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 provides the parameter 'entry' with type and maxLength, and the description adds meaningful constraints on content (e.g., not including conversation details). The tool description also reinforces the purpose of the parameter, going beyond the schema's basic info.

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 metaphorically indicates the tool's purpose of writing an entry (up to 500 characters) into a guestbook. It clearly states the action ('write') and the resource ('book'), though it could be more explicit. It is not a tautology and conveys the core function.

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 provides some guidance on when to use the tool: it is optional ('Nothing asks you to'), non-critical ('nothing depends on it'), and for human reading later ('read by a person eventually'). However, it does not explicitly name alternative tools or compare with siblings, leaving some inference needed.

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