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

Beyond the annotations (readOnlyHint, idempotentHint, openWorldHint), the description discloses the privacy-critical behavior that record content is never transmitted, only its digest, and that the result is a compact JWS verifiable against a named JWKS endpoint. It does not discuss key rotation, token lifetime, or any rate/authorization constraint on calling the remote authority, so it stops short of full behavioral disclosure.

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?

Four dense sentences, front-loaded with the core action and the verification URL, then the workflow, then the mode switch, then the scope exclusion. The long parenthetical with the well-known-keys URL slows the opening but carries useful verification information rather than 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?

For a three-parameter tool with no output schema, the description covers the call contract: what goes in (hex digest only, or a token), what comes back (a compact JWS), how to verify it, and what the tool is not. The unexplained purpose enum and the lack of any guidance on interpreting a failed token verification are the remaining holes.

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 67%, and the description meaningfully reinforces sha256 (must be the hash of a canonical record you compute, lower-case hex) and token (verification path). The purpose parameter, which carries an enum with no schema description, is never explained in the description — a real gap given its two distinct values (callback-record vs 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?

The description states a precise verb and artifact: produce a signed timestamp (compact JWS, EdDSA) over a SHA-256 digest, with the key URL for verification. It also scopes itself by excluding RFC 3161, so an agent can tell it apart from a generic timestamping service or a certificate-issuing tool without inspecting 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?

It gives a concrete motivating use case (make a callback record or approval tamper-evident), an operational instruction (hash the canonical record yourself, pass only the 64 hex chars), and a mode switch (pass token instead to verify an earlier timestamp). What's missing is any pointer to which sibling verifies a record's signature versus a timestamp, leaving the boundary to the agent's inference.

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