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

The annotations already declare read-only, idempotent, open-world, and non-destructive behavior, and the description adds substantial context beyond that: retention for 7 days, the closed envelope shape, leaf hashing with sha256(0x00 || canonical envelope), audit-path root rebuilding, and Ed25519 signature verification. It stops short of describing error behavior when an envelope is expired, missing, or fails verification.

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?

The description is front-loaded with the return action and audit path, then explains the verification steps, and ends with the admission-version context. It is dense but not wasteful; each sentence contributes relevant technical meaning.

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 two-parameter read-only tool with full schema coverage and an output schema, the description supplies enough behavioral context about retention and verification. It does not cover failure modes or explicit routing relative to sibling tools, but it is complete enough to invoke correctly.

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 parameters, including the UTC day format and leaf index range. The description adds slight context by saying the day must be closed and the envelope is kept for 7 days, but it does not add syntax or constraints beyond the schema.

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: return envelope i of a closed UTC day, with its RFC 6962 audit path. It clearly distinguishes a leaf/envelope from broader day or ledger records, but it does not explicitly name a sibling tool or explain when this should be chosen over them.

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 reference to a closed UTC day, retention of 7 days, and admissions naming a check by its digest. However, there is no explicit when-to-use guidance, no exclusions, and no direct comparison with alternatives such as the related day or ledger tools.

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