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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds information the annotations cannot: it is public with no bearer required, the substrate performs the fetch, and the return is the `verify_credential` envelope plus `credential_url` and `credential_bytes`. It also documents the silent-failure mode caused by body paraphrasing, which is genuinely actionable.

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 when-to-use clause plus the key differentiator, and the rest supports it with concrete detail. It is somewhat long and restates the URL-vs-body point twice, which costs a little, but nothing is truly wasted.

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, the description still specifies the return shape (same envelope as verify_credential plus two extra fields), the auth posture (public), and the required inputs. Nothing an agent needs to invoke and correctly interpret this tool 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 coverage is 100%, so the schema already documents both params (including jwks_url's optional derivation behavior), giving a baseline of 3. The description adds meaning beyond the schema by insisting that only the URL is passed — never the JSON body — and that `credential_url` points at a credentials.json or single-VC document.

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+resource (verify a credential by URL) and crisply distinguishes itself from the sibling `verify_credential`: the difference is that the substrate fetches the body, so only the URL is passed. An agent can select between the two without opening either 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?

Explicit when-to-use conditions are given: prefer this when calling from LLM brains, when the credential is too large to forward verbatim, or when the client might paraphrase/trim the body. It also names the failure mode that tempts the wrong choice (paraphrasing breaks JCS canonical form and yields a false `valid: false`) and the sibling that is the alternative.

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