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

No annotations are provided, so the description carries the full burden. It discloses merge semantics ('without touching the others'), that the value is never echoed back, and the required authentication proof (nsec-signed kind-27235 or cached dpop_token phrase). It also explains the destructive consequence of the alternative to justify the tool's existence, which is rich behavioral context beyond the structured fields.

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 front-loaded with a clear purpose and every sentence contributes meaningful context: merge behavior, security restrictions, value handling, and comparison to the alternative. It is slightly verbose (five sentences) but contains no fluff or repetition that could be trimmed without losing value.

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?

Despite lacking annotations, the description comprehensively covers purpose, use case, security requirements, behavioral specifics, and alternative comparison. The presence of an output schema (as indicated) means return values need not be described. For a tool of this complexity, it provides all necessary context for correct 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?

Schema description coverage is 100%, with each parameter (field, value, dpop_token) having descriptive text. The tool description adds minimal param-specific detail beyond the schema; the example mentions 'btcpay_api_key' but does not add new syntax or format information. The baseline of 3 is appropriate because the schema already handles parameter documentation.

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 a specific verb and resource: 'Add or update a single operator secret field.' It clearly differentiates from the sibling tool 'schwab_update_patron_credential' by specifying 'operator' and from a full bundle re-delivery by calling itself the 'field-level counterpart.' The scope is unambiguous: one secret field, not the whole credential bundle.

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 states when to use the tool: to rotate one secret without restating unchanged fields. It names the alternative (re-delivering the whole bundle over Secure Courier) and explains the downside of that alternative ('any field omitted from a courier reply is destroyed'). It also clearly restricts usage to operators and rejects patron proofs, guiding correct selection among siblings.

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