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

No annotations are supplied, so the description carries the full behavioral burden and does so: input acceptance rules (PEM single or full chain, leaf first, ≤32KB), the auto-detection rule for the GM branch (signature OID under 1.2.156.10197), the exact can_sign_child logic with an RFC 5280 citation and its edge case (missing keyUsage is not a restriction), the fact that chain linkage is structural only and not signature validation, and the failure mode ('Certificate parse failed'). It even discloses the underlying implementations (cryptography for the international path, GmSSL C library for SM2 points).

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 and limits are front-loaded, which is good, but the body is a single dense paragraph that enumerates every returned field in a run-on list. Much of that enumeration is justified because there is no output schema, yet the lack of any structural separation makes it hard to scan and pushes it well past the minimum useful length.

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 and no annotations for a fairly complex tool, the description compensates fully: it documents return-field families for both single-cert and chain output, the meaning of chain_linkage states, the dual SHA-256/SM3 fingerprints, the GM-only SM2 public key encodings with exact lengths, and the error condition. An agent can predict the response shape without an output schema.

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 and schema coverage is 100%, with the schema already stating the PEM framing and the 32KB multi-cert allowance, so the baseline is 3. The description reinforces leaf-first ordering and the failure condition but adds little syntax or formatting detail the schema does not already carry.

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 opens with a specific verb and resource (parse an X.509 certificate or chain), names both code paths it covers (international X.509 and GM/SM2), and states the scope precisely — leaf-first multi-cert PEM up to 32KB, with top-level fields describing the first certificate. This is far beyond restating the name and lets an agent distinguish it from sibling parsers immediately.

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 explicitly routes structural-only work here and signature verification to cert_verify ("结构展示，不含签名验证；逐级签名验证用 cert_verify"), and the schema note adds the size distinction (chain ≤32KB here vs single ≤10KB for cert_verify). What it lacks is an explicit "use this when / do not use when" framing against other parse siblings, so it stops just short of a 5.

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