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

Annotations only declare openWorldHint=false and destructiveHint=false, so the description carries the real behavioral burden — and does: the buyer is emailed the message plus the user's contact details (an irreversible external side-effect), one response per ad, and a 20/day rate limit. This is exactly the kind of context annotations can't express.

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, no filler, and the action is front-loaded before the caution and the quota. Every sentence earns its place.

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?

Covers the action, eligibility, side-effect, duplicate limit, and rate limit — ample for a 4-param mutation tool with no output schema. The only omission is what the agent gets back on success, which the description could briefly note since no output schema exists.

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%, documenting id, contact, message, and asking_price thoroughly, so the baseline is 3. The description adds a little semantic intent ('saying they have the item', 'open to offers' is already in schema), but no real parameter detail beyond 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?

States a specific verb (respond) on a specific resource (someone else's open wanted ad) on the user's behalf, with the outcome (saying they have the item). The 'someone else's' framing clearly separates it from siblings like reply_to_response and my_responses.

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?

Explicit when-to-use constraint: 'only use this when the user actually has (or can get) the item and has asked to respond.' It does not name the neighboring alternative (reply_to_response) as an explicit contrast, so not a full 5, but the eligibility condition is unambiguous.

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