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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description still adds real behavioral information beyond them: it validates the signature and reports the result, and it refuses private keys, which prevents a plausible misuse. It does not say what happens on malformed input, but that omission is minor.

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?

One sentence, front-loaded with the verb and resource, then a compact list of returned fields, closing with the one hard constraint. No filler or redundancy.

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 carries the burden of indicating what comes back, and it does so by enumerating subject, names, key details, signature algorithm and verification status. The only soft spot is the vague term 'findings', which is not defined, and no note on how invalid or non-CSR input is reported.

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?

There is a single parameter with 100% schema coverage, and the schema description already spells out the exact PEM armor delimiters and the 20000-character cap. The description contributes only the word 'pasted' and the fact that it must be a CSR rather than a certificate, so the schema is doing most of the work.

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 ('Decodes a ... CSR') and then enumerates exactly what is extracted: subject, names, key type and size, signature algorithm, verification status, findings. The explicit framing as a certificate signing request distinguishes it from the adjacent ssl_certificate_decoder, which handles issued certificates.

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 rather than stated: the word 'pasted' signals the input must be pasted PEM text, and 'Private keys are refused' tells the agent one case where the call will fail. There is no explicit when-to-use versus ssl_certificate_decoder guidance and no statement of what to do with a non-CSR PEM block.

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