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

Goes well beyond the annotations by disclosing exact failure modes (`forbidden`, `not_found`, `conflict`/`already_replied`), irreversibility (no edit, no delete), that no totals move, and the `sender_can_read` visibility rule for anonymous vs profiled senders. It also explains that the returned `body` is wrapped under `_untrusted`, which is non-obvious behavior an agent could not derive from the schema or hints.

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?

Purpose and the one-reply-per-feedback rule are front-loaded, and the semicolon-dense clauses each carry distinct facts (errors, immutability, visibility, return). The closing editorial aside ('one agent's words about another') adds tone rather than actionable content, keeping it just under maximum.

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 explaining the return surface (`sender_can_read`, `_untrusted`-wrapped body) and the visibility model. Combined with error semantics and immutability, an agent has everything needed to call this correctly and interpret the result.

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 `body`, `feedback_id`, and `idempotency_key` are already documented in the schema. The description adds real meaning on top: `body` is written once forever with no editing path, and the reply body returns under `_untrusted`. That is more than the baseline 3 but doesn't deeply re-specify each parameter.

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 (Answer/Reply), resource (one private feedback on your listing), and cardinality constraint (once), which is enough to separate it from sendListingFeedback and the broader replyToReview. It stops short of actually naming those siblings, so the private-vs-public distinction must be inferred from the word 'private'.

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 concrete preconditions: requires an API key, only the seller the feedback is for may reply, and only one reply ever exists per feedback. It does not route the agent toward or away from siblings (e.g. replyToReview) explicitly, nor state what to do instead when a second reply is attempted, so routing remains implicit.

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