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

Annotations already declare readOnlyHint/idempotentHint/openWorldHint=false, so the safety profile is covered. The description usefully adds that the call does no page fetching and returns three artifacts including a missing-fields list, which tells the agent to expect partial output rather than a validation error.

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?

Three short sentences, zero filler, with the output contract stated first and the usage caveat second. Every sentence earns its place.

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?

An output schema exists so return values need not be explained, and annotations cover the safety profile. For a two-parameter, read-only builder the description supplies everything an agent needs: what it produces, when to use it, and that it performs no fetching.

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 50%: the enum on `type` is self-documenting and `values` carries a schema description about repeatable fields being arrays. The description adds nothing about parameter shape, formats, or how `values` keys must match the chosen type, so it neither compensates nor regresses. 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?

Specific verb and resource: builds schema.org JSON-LD for a single type, and it names its outputs (script tag, missing-fields list). An agent can distinguish it from conversion siblings like build_open_graph, though the description never explicitly contrasts with the closest neighbour. Clear, but not maximally differentiated.

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?

"Use this when you already know the fields" gives a real selection condition, and "It does not fetch a page" excludes the fetch-based siblings (fetch_page_markdown, inspect_meta_tags) by implication. It stops short of naming the alternative tool an agent should use when it does not already know the fields.

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