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

Adds substantial behavior beyond the annotations: a pass 'moves the brand's rows from listed to claimed', a seat key is issued, every claim is logged, and verification is explicitly a human step. It does not cover permissions, rate limits, or what happens to a seat key that is reused. Note a mild tension with openWorldHint=false, since the challenge relies on DNS TXT records for arbitrary external domains and GTIN resolution on gtinfetch.ai, but this is not a direct contradiction of the stated 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?

Dense but nearly every clause carries unique information, and the workflow is front-loaded in the first two sentences. The long parenthetical enumerating category routing rules is hard to parse on first read and could be broken out, but it earns its place given the branching logic involved.

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 all three invocation modes of a genuinely complex tool and explains what an accepted claim returns in kind ('answers a challenge', 'answers the seat key') even though an output schema exists. Combined with the rejection rules and the explicit note that verification is never a tool step, an agent has enough to call this correctly.

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 0% schema description coverage the description must carry all parameter meaning, and it does for four of five: card_url (the agent's card, whose domain is challenged), gtins (GTINs the brand claims), challenge_id (returned by an accepted claim), and seat_key (unlocks rows editing). Only 'rows' is left semantically thin - we learn it sets price, availability, markets and claims for the seat's own GTINs, but nothing about the shape of each row object.

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?

Opens with a specific verb and resource: 'A brand's agent claims its seat on A2A Grocery', then names the two inputs that define the claim (card URL and GTINs). It is clearly distinct from siblings like verify_gtin or resolve_actor, though the multi-phase nature (initial claim, challenge answer, seat update) makes the single core action slightly diffuse.

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?

The description effectively encodes the call sequence: first with card_url plus gtins, then again 'with the challenge_id once it is published', then with seat_key and rows. It also states rejection conditions (unresolved GTIN, beer/wine/spirits) and routing to other registries. It stops short of naming sibling tools to use instead, so routing is to external registries rather than to the provided alternatives.

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