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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety and determinism profile is fully covered structurally. The description adds only the notion of 'canonical' URLs and a 'human fallback', but says nothing about auth requirements, rate limits, or stable-vs-mutable URLs. With annotations carrying the burden, a 3 is appropriate.

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?

A single front-loaded sentence with no filler; the verb and the return payload are stated immediately and every noun 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?

With no output schema and no parameters, the description sensibly enumerates the categories of URLs that come back, which is the main thing an agent needs. It could go slightly further by describing the shape/keys of the response or stability guarantees, but it is adequate for a zero-arg discovery endpoint.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline is 4. Schema coverage is also reported at 100%, leaving no gap for the description to fill.

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 ('Return') and a precisely scoped resource ('canonical machine-readable URLs'), then enumerates exactly which URL kinds are returned (InstaVeil x402, OpenAPI, llms.txt, human fallback). This is unmistakably distinct from the sibling product/purchase tools.

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?

Usage is implied by the nature of a discovery/entry-point endpoint, and an agent can infer it should be called to bootstrap knowledge of the service. However, the description never states when to call it, whether it is a prerequisite for other tools, or any alternative — no explicit guidance.

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