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

Annotations only give readOnlyHint=true and openWorldHint=false; the description adds material context beyond them: no network fetch, no API key required ("Works with no key"), the returned keys (jsonld, script, missing, problems, recommended, fields), and the failure behavior for an unsupported type. Nothing contradicts readOnlyHint — the tool generates output rather than persisting it.

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?

Terse labeled sections (When / Instead / Inputs / Returns / Fails) front-load the purpose and alternative before any parameter detail. Every line carries information — no filler, no restatement of the title.

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 3-parameter generator with no output schema, the description covers what it produces, the exact return keys, the error path, and the no-auth condition. An agent has everything needed to call it correctly on the first attempt.

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%, so the baseline is 3, but the description adds real meaning: `type` must be one of the offered enum values, `as` narrows to a concrete subtype like Plumber, and `fields` takes values by key as text with "Give only what the page shows." It also explains the non-obvious pattern of calling with only the required `type` to discover fields.

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 artifact: "Makes JSON-LD for one page from the fields given, ready to paste." It also bounds scope with "fetches nothing" and explicitly separates itself from the sibling clickd_check, so an agent can pick it 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?

Uses explicit When/Instead structure: use it "to write the structured data a fix asks for," and use clickd_check with kind product for checking a live product page. It also gives a discovery trick ("call it with only type to see the fields") that no alternative tool provides.

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