Open PKCS#12 (MAC, decryption, non-extractable key import, certificates; optional PEM bundle)

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

Goes well beyond the annotations: discloses that keys enter the host as non-extractable and are never exported, that no result contains key bytes or the password, that calls with a password are never cached, and that a negative verdict is a report rather than isError. It maps each failure mode (wrong password, legacy RC2/3DES, missing MAC, unspecified RSA scheme) to a specific reason code, which annotations cannot express.

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?

Front-loaded with the core operation and verdict semantics, and nearly every sentence carries a distinct behavioral fact. However, the single long run-on paragraph is dense, and rsaScheme/allowUnverifiedIntegrity/exportCertificates semantics are largely repeated from the schema descriptions, so a little trimming is possible.

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 15-parameter tool with a nested file object, an output schema, and non-obvious state effects (non-extractable key import), the description covers password sourcing, integrity-verification outcomes, export restrictions, caching, and the absence of key material in results. An agent can decide whether, how, and with what caveats to call it without further reading.

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 baseline is 3, but the description adds consequence-level meaning: rsaScheme has no default and an RSA key without it yields PKI_REASON_PKCS12_RSA_SCHEME_UNSPECIFIED with signingKey null; a password may come from PKINATIVE_MCP_PASSWORD instead; verbosity 'summary' keeps only scalars. Some parameters (limits, fields, pemMode, encodingRules) are not discussed in the description, leaving the schema to carry them.

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 (open) and resource (PKCS#12 .p12/.pfx), and enumerates the concrete work performed: MAC verification, PBES2 decryption, non-extractable key unwrap, certificate parsing, CRL counting. It also names the sibling inspect_pkcs12 and the difference between them, so the agent can distinguish the two without opening a 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?

Explicitly says 'Prefer inspect_pkcs12 first' with the reason (it describes MAC kind and bags without a password), and gives conditional guidance for allowUnverifiedIntegrity (trusted origin only) and exportCertificates (only from a file that opened). When/when-not conditions are spelled out rather than implied.

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