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

Goes well beyond the readOnlyHint/openWorldHint annotations: it enumerates the returned fields, calls out what is omitted (pay, description), discloses that text is employer-language/usually Japanese, and explains the x402 payment model including that failed calls are not charged. That is exactly the extra context annotations cannot carry.

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?

Front-loaded with the resource and origin, then fields, then omissions, then pricing. The opening sentence is a long comma-spliced list, but essentially every clause carries new information an agent would otherwise lack.

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?

For a single-parameter read-only feed with an output schema, this covers everything an agent needs: source, geography bias, returned and missing fields, language caveat, and the payment prerequisite for invoking it.

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% and the single 'limit' parameter already documents its 1-50 range and default of 10. The description adds nothing about the parameter, so baseline 3 applies.

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 ('newest job postings/projects from Wantedly's public projects API') with a scoping qualifier ('mostly Japanese employers'). The Wantedly/Japan framing lets an agent distinguish this from the dozens of sibling job-board tools without opening the schema.

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 'mostly Japanese employers' qualifier gives clear selection context against sibling boards, and 'Pay and description are not returned' steers the agent away when compensation or full text is needed. It stops short of naming an alternative tool or stating explicit exclusions, so it is not a 5.

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