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

Annotations already declare readOnlyHint and openWorldHint, so the bar is lower, and the description still adds the operationally critical detail that each call costs $0.02 in USDC on Base via x402 — a real payment/auth prerequisite an agent must know before invoking. It also discloses the shape of what comes back, though it says nothing about failure modes, rate limits, or empty-result behavior.

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 dense sentences: the payload and its fields come first, the cost model last. No filler, no restating of the tool name, and the parenthetical explaining Reverb earns its place for agents unfamiliar with the marketplace.

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?

There is no output schema, and the description compensates by describing the return contents in detail (median asking price by condition, share taking offers, top makes, cheapest with postage, plus listing fields). For a seven-parameter search tool this is close to complete; only pagination and error/empty-result handling are unaddressed.

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?

With 100% schema description coverage the schema already documents all seven parameters, so the baseline applies. The description adds marginal meaning — 'up to 100 listings' clarifies the max ceiling and 'cheapest with postage' hints at what the shipsTo filter surfaces — but it does not explain how priceMin/priceMax interact with currency or how condition filtering affects the median calculation.

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 ('Live Reverb ... listings for a keyword') and names the marketplace with a parenthetical gloss, which cleanly separates it from the sibling marketplace searches (ebay_market, poshmark_search, vinted_search). It goes further by enumerating both halves of the payload: the market summary and the listing fields.

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?

Usage is implied rather than prescribed: an agent can infer this is the Reverb-specific marketplace search, and the stated $0.02 cost gives a decision factor, but there is no explicit when-to-use/when-not or a named alternative to route to when the user wants a different marketplace or a non-gear search.

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