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

Annotations cover the safety profile (readOnly, non-destructive, non-idempotent), and the description adds value beyond them: block-style/no-folding output shape, 100 KB limit, 400-on-invalid-JSON with no charge, pricing and first-25-free, and the note that repeats are charged because each call costs — which coherently explains idempotentHint=false.

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 conversion and format details, then the routing hint, then limits and pricing. It is dense but every sentence conveys actionable information; the pricing/credits clause is a little promotional ('Price $0.01/call via x402 USDC or a card key (/credits)') and could be trimmed without loss.

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, no-output-schema conversion tool this covers input limits, error semantics, output style, and cost. The only modest gap is a precise statement of what the returned YAML document contains (bare document vs. trailing newline, multi-document handling), though 'block style, no line folding' already sets expectations.

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% with a single required 'json' string parameter, so the baseline is 3. The inline worked example (json={"name":"agent","ports":[80,443],"enabled":true}) usefully shows that the parameter takes a JSON *string* rather than a structured object, which is the one ambiguity the schema type alone leaves.

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 ('Convert a JSON value into a YAML document'), pins the output style (block style, no line folding), and names the sibling for the reverse direction (yaml_to_json). An agent can distinguish it from json_format, json_minify, and yaml_to_json without opening any 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?

Gives the positive condition ('use when a tool or person wants YAML'), the explicit exclusion/alternative ('for the reverse use yaml_to_json'), and names target use cases (config files, K8s manifests, GitHub Actions). Also states the 100 KB input ceiling, which is a real gating condition.

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