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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior. The description adds value beyond them by disclosing the output shape (a hex digest) and misuse boundaries (not for password storage or key derivation, no secrets as input), which the annotations do not imply. It does not discuss limits such as the 4096-char cap, but that is already in the schema.

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?

Two dense sentences with no filler: the purpose and algorithm options come first, then routing to the alternative, then the return format and prohibitions. Every clause 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?

For a two-parameter, annotation-covered tool with no output schema, the description supplies everything an agent needs: what it does, when to prefer the sibling, what it returns, and the safety caveats around secret content. Nothing material 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%, so both parameters (algo enum, text) are fully documented in structured data. The description names the same algorithms already enumerated in the schema and reinforces the non-secret input intent, but adds little parameter meaning beyond that. Baseline 3 applies when the schema carries the load.

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 and resource ('Compute SHA-256 or legacy MD5 text digests') and explicitly distinguishes itself from the sibling generate-token, which creates new IDs rather than deriving digests. An agent can separate this from the other generate-* tools without opening any 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?

Gives positive guidance ('use for non-secret content fingerprints'), names the competing sibling and what it is for instead, and adds a negative constraint ('unsuitable for password storage or key derivation'). Both when-to-use and when-not-to-use are covered explicitly.

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