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

With no annotations, the description carries the full burden and excels: it discloses the authorization model, the proof mechanism, that the private key is never transmitted, immediate cutover timing, that the retired key authorizes nothing after commit, and that replacement is irreversible. This is far richer behavioral disclosure than typical tool descriptions.

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?

Three dense sentences with zero waste: the core action is front-loaded, followed by the authorization/proof mechanics, then the behavioral consequences. Every sentence earns its place and no information is repeated from the schema.

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?

Comprehensive for a security-critical, irreversible mutation with no annotations: authorization, proof requirements, cutover semantics, and irreversibility are all covered. The only gap is that no output schema exists and the description does not explain what the tool returns on success or how failures surface, which an agent would need for post-call handling.

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 the schema already documents all three parameters in detail (key format, proof type, timestamp tolerance). The description adds marginal reinforcement (e.g., 'never sent here') but does not meaningfully extend what the schema provides, landing at the baseline of 3.

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 ('Replace the subject's active signing credential') that unambiguously identifies the operation. 'Replace' clearly differentiates this from the sibling revoke_credential, and 'signing credential' names the exact resource affected.

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?

The authorization prerequisite (current signing credential must authorize) gives implied context for when this tool applies, but no explicit when/when-not guidance is given. The sibling revoke_credential is the obvious alternative for a different credential lifecycle operation, yet it is never named or contrasted.

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