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

Annotations already cover the safety profile (readOnlyHint=true), so the description's job is to add context — and it does, disclosing the ownership restriction and the exact content surface returned, including an unread count on the private thread. It omits pagination or volume behavior for what could be a long response list, which keeps it out of 5 territory.

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?

Two sentences, zero filler: the first leads with the action and the resource, the second carries the hard constraint. No restatement of the title and no redundant verbs.

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 correctly compensates by enumerating the returned fields, and with one simple parameter the input side is fully covered. What is missing is any hint about result size, ordering, or pagination for a list that could grow large.

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 single parameter documents its own provenance ('from post_want or my_wants'). The description adds only the qualifier 'one of the user's own wanted ads,' which reinforces the ownership rule but provides no additional format or lookup semantics 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 and resource ('Read the responses sellers have sent to one of the user's own wanted ads') and enumerates the returned payload (seller name, message, contact details, asking price, photo, private thread, unread count). This is far more specific than the sibling names alone and lets an agent distinguish this received-responses read from neighbors like my_responses or search_wants.

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?

Gives a clear applicability constraint: 'Only works for the user's own ads,' which functions as a when-not condition and tells the agent this cannot be used on others' ads. It stops short of naming an alternative tool (e.g., my_responses for responses the user sent), so it is clear context rather than full routing guidance.

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