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

No annotations are present, so the description carries the full burden. It reveals merge semantics ('without touching the others'), security restrictions ('RESTRICTED to the operator... patron proofs are rejected'), and that 'The value is never echoed back'. It doesn't cover side effects like invalidation, but the key behaviors are disclosed.

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 well-organized paragraphs. The first sentence states the purpose, the second explains the alternative scenario, and the third covers security. Each sentence earns its place, though the example and some phrasing add slight 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?

This is a mutation tool without annotations but with an output schema. The description covers usage, merge semantics, security requirements, and the distinction from sibling tools. It doesn't explain error handling or idempotency, but it provides enough context for correct selection and invocation.

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?

Input schema descriptions cover all three parameters (field, value, dpop_token) with meaningful details, so the baseline is 3. The description adds a concrete example (btcpay_api_key) and context for dpop_token, but doesn't materially exceed schema coverage.

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 'Add or update a single operator secret field', a specific verb+resource. It also distinguishes from the whole-bundle re-delivery via Secure Courier, clarifying its unique scope.

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 positions itself as 'the field-level counterpart to re-delivering the whole bundle' and says 'Use it to rotate one secret'. It describes the scenario where a courier reply would destroy omitted fields, giving a concrete when-to-use condition.

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