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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered; the description adds genuinely new behavior: it accepts JSON or YAML, it will attempt to discover the spec under a site, and it costs $0.004 USDC per call via x402. It omits what happens when no spec is found and how 'limit' truncates results.

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 purpose, then the extracted fields, then the value proposition and price. Three sentences with no filler, though the long comma-separated field list could have been structured more scannably.

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, enumerating the returned fields is the right move and is largely covered here, and the x402 cost is disclosed for a paid tool. Gaps remain around the 'limit' parameter, discovery/error behavior when no spec exists, and target-API auth requirements beyond merely reporting schemes.

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 0%, so the description must carry the burden. It does clarify the 'url' parameter somewhat (a spec in JSON/YAML, or a site under which the spec is searched), but adds nothing about the 'limit' parameter or its units/truncation behavior.

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?

Names a specific verb ('understand') and a specific resource (OpenAPI/Swagger spec) and then enumerates exactly what it extracts — title, version, servers, auth schemes, operations with parameters/body/auth/tags, schema names. This clearly separates it from raw-fetch siblings like http_inspect or contract_inspect.

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?

States a clear use case: 'The fastest way for an agent to learn a new API.' It also notes the fallback behavior when no spec URL is known ('or we look for it under the site'). It names no explicit alternative sibling or exclusion condition, so it stops short of a 5.

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