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

No annotations are provided, so the description must carry the full burden of behavioral disclosure. It explicitly says 'Free, no extra charge', which discloses cost, and uses the verb 'Check', which strongly implies a read-only operation with no side effects. It also hints that the tool only returns information (status, escrow, result availability) rather than causing changes. While it doesn't explicitly state 'does not modify anything', the language is clear enough for a simple query tool.

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?

The description is concise, with the main purpose stated first and requirements after. The slight redundancy in 'Free, no extra charge' is minor but costs a tiny bit of conciseness. Overall, every sentence earns its place and the structure is front-loaded.

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?

The tool is simple: three string parameters, no output schema, no nested objects, no annotations. The description covers what the tool does and what inputs are needed, and it implies the output content by naming status, escrow, and result availability. It does not explicitly describe return values or error conditions, but given the low complexity, the description is adequate for an agent to call the tool 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?

Schema description coverage is 0%, so the description must compensate. It adds meaningful context by stating which parameters are required and specifically notes that api_key comes from marketplace_register, which is useful provenance information. The parameter names themselves are self-explanatory (agent_id, api_key, contract_id), and the description confirms their role. It does not fully elaborate each parameter, but for such simple string types, this is sufficient compensation.

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?

The description clearly states a specific verb ('Check'), a specific resource ('one of your contracts'), and the exact information it provides (status, escrow, result availability). This distinguishes it from related siblings like marketplace_get_result, which retrieves the result itself, and marketplace_my_sales, which lists contracts.

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 gives clear context: it is for checking your own contracts, including their status, escrow, and result availability. It also states the required credentials and their origin ('api_key from marketplace_register') and adds that there is no extra charge. It does not explicitly name alternative tools or conditions for when not to use it, but the purpose is distinct enough that an agent can infer when this is the right tool.

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