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

With no annotations, the description carries the full behavioral burden. It discloses that the operation merges without touching other fields, that the value is never echoed back, and that restricted operator proof (nsec-signed kind-27235 or cached dpop_token) is required. It also explains the destructive alternative, adding safety context.

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 description is efficient and well-structured. The first sentence states the purpose, subsequent sentences cover behavioral nuances, usage context, and security constraints. Every sentence earns its place without redundancy.

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?

The description fully addresses the tool's complexity: merge behavior, use case, security restrictions, and proof requirements. With an output schema present, omission of return details is acceptable. It is comprehensive for a 3-parameter tool.

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 baseline is 3. The description adds meaning beyond the schema by giving a concrete example ('btcpay_api_key'), clarifying the merge semantics for 'field', and elaborating on the 'dpop_token' proof types (nsec-signed kind-27235 or cached phrase). This exceeds the schema's descriptions.

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,' which precisely states the verb (add/update), resource (operator secret field), and scope (single field). It distinguishes itself from sibling tools like excalibur_update_patron_credential by focusing on operator credentials and from whole-bundle delivery by noting it is field-level.

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 description explicitly explains when to use this tool: to rotate one secret without restating unchanged fields and avoiding the destructive behavior of omitted fields in a courier reply. It also states a clear exclusion: patron proofs are rejected, implying this is only for operator use. This is strong usage guidance.

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