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

Annotations only mark this as non-destructive and closed-world, but the description adds critical behavioral context: the message is private, the other person is emailed, and only user-requested content should be sent. This goes well beyond the annotations and directly informs safe invocation.

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 sentences, front-loaded with the core action. The second explains scope, the third adds workflow and caution, with no redundant or filler content.

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 two-parameter messaging tool with no output schema, the description covers purpose, audience, side effect (email notification), safety caution, and parameter sourcing. Nothing important is missing for correct invocation.

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%, so the baseline is 3. The description adds meaningful guidance by telling the agent where to obtain the response_id (get_responses or my_responses), which is not in the schema, while the body parameter remains adequately documented in 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?

The description states a specific verb and resource: 'Send a private message in the conversation on a response.' It clarifies the tool's role for both buyer and seller, making it easy to distinguish from initial response tools like respond_to_want.

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?

It specifies the audience (buyer replying to seller, seller replying to buyer) and tells the agent where to get the required response_id from get_responses or my_responses. It does not explicitly exclude or compare against sibling tools like respond_to_want, but the context is clear.

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