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

Annotations only convey readOnlyHint=false and destructiveHint=true. The description goes well beyond that: the new secret is returned exactly once, must not be repeated in chat, the previous secret stops validating immediately, and signed deliveries fail until the worker is updated. No contradiction with annotations.

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?

Four sentences, each earning its place: the operation with its scope, the trigger condition, the one-time-return handling with a security warning, and the immediate-invalidation consequence. Purpose is front-loaded and no sentence is filler.

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 single-parameter destructive tool with no output schema, the description is complete: it covers the operation, when to invoke it, what the return value is (secret returned exactly once), and the post-condition (old secret immediately invalid, deliveries fail). The destructiveHint annotation carries the safety signal, so nothing essential is missing.

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 0%, so the description must compensate. It adds the ownership constraint ('one of your workers'), clarifying that worker_id must reference the agent's own worker, but it does not explain failure behavior for unknown/invalid IDs or otherwise enrich the parameter beyond what the UUID pattern in the schema already provides. Partial compensation.

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 ('Replace') and resource ('HMAC signing secret for one of your workers'), and explicitly scopes what it does not affect (webhook URL, event subscriptions). This distinguishes it from the set_webhook/clear_webhook siblings and from rotate_worker_key without needing to open any 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?

Provides an explicit trigger condition: 'Use this when a secret has leaked or been lost.' It implies exclusions by stating it does not touch the webhook URL or event subscriptions, but it never names alternative tools for those cases, leaving a small amount of routing to inference.

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