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

With no annotations at all, the description carries the full burden. It usefully reveals that this is a hosted/remote service and warns that submitted key material leaves the caller's environment, plus it discloses the comparison algorithm. It does not say what the result looks like (a boolean match? per-pair fingerprints?), whether material is retained, or what happens when the inputs are encrypted keys without a password.

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 purpose statement is front-loaded and the security warning follows immediately; there is no filler. The cost is a fully duplicated bilingual warning that doubles the length, though for a safety-critical notice that repetition is defensible.

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?

Given five parameters, no output schema, and no annotations, the definition is nonetheless sufficient to call correctly: the mechanism, the required inputs, and the security constraint are all stated. The main missing piece for a match-verification tool is the shape of the response, which is not strictly required to invoke it.

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 80% and the PEM fields are self-documenting, so the baseline is 3. The one meaningful gap is the required 'mode' parameter: its three enum values (cert-key, cert-csr, key-csr) implicitly define which other fields are mandatory, but neither schema nor description states that mapping, and 'password' is only marked optional in the schema, not explained in the description.

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 names a specific operation and its inputs (certificate / private key / CSR matching) and discloses the underlying mechanism (SubjectPublicKeyInfo SHA-256 fingerprint comparison), which distinguishes it from the sibling decode/inspect tools. It stops short of explicitly contrasting itself with cert.decode, csr.decode or convert.run, so an agent must infer the boundary rather than being told.

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?

There is a hard usage constraint (test material only, no production private keys or passwords), which is genuine guidance about when this tool is safe to call. However, nothing explains when to prefer this over cert.decode/csr.decode/convert.run, and nothing tells the caller which of the three modes applies to which situation.

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