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

Beyond the annotations (readOnly, idempotent, openWorld, non-destructive), it discloses side-effect and auth facts an agent cannot get from structured fields: it reads exactly one public file, stores nothing, calls no checkout endpoint, and needs no API key. That directly answers the safety and permission questions for a fetch tool.

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 what the tool is and where it looks, then the two input modes, then side effects and auth. Every sentence carries distinct information with no filler.

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?

Even though an output schema exists, the description still names the return shape (verdict, per-rule results, fix list with the change that fixes each failure), and covers inputs, safety, and auth. Nothing needed to invoke it correctly is missing.

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 100% and the schema already explains that document is checked without a fetch, so the description adds little beyond restating the fetch-vs-paste distinction. Baseline 3 is appropriate when the schema carries the parameter semantics.

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?

The description states a specific verb and resource — validating a store's UCP discovery file at /.well-known/ucp — which is concrete and unambiguous. It does not explicitly differentiate itself from the sibling acp.validate, so an agent must infer the UCP-vs-ACP split from the protocol name rather than being told.

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?

It clearly routes the two input modes: pass url to fetch a public store's file, or document to check pasted JSON. That is actionable context, but there is no explicit when-not-to-use or pointer to acp.validate for the other protocol.

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