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

With no annotations, the description carries the full burden and does well: it discloses merge semantics ('without affecting other fields'), cost ('Free'), and an authentication requirement ('Proof of npub ownership is required'), plus the sensitivity of the write target. It omits error behavior, rate limits, and whether a new field is created versus only updated.

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?

Front-loaded with the core action, and each subsequent sentence adds distinct value (merge behavior, examples, cost, auth). Slightly fragmented by line breaks but no filler or 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?

An output schema exists, so return values need no explanation, and the description covers the key non-obvious facts: merge behavior, cost, and proof-of-ownership auth for a sensitive write. It is complete enough to invoke correctly, with only minor gaps around failure modes.

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%, including a detailed dpop_token spec, so the schema does the heavy lifting and the baseline is 3. The description references 'field' and 'value' conceptually but adds no format, allowed values, or syntax beyond what the schema already documents.

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 — 'Add or update a single patron credential field' — and immediately scopes it ('single field', 'merges into existing'). An agent can distinguish this from siblings like beesknees_update_operator_credential and beesknees_delete_patron_credential without opening 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?

Gives concrete use cases ('setting an account identifier after OAuth, changing a default brain'), which clarifies when to reach for it. However, it does not name a sibling alternative or state when-not to use it (e.g. vs delete/forget or bulk receive_credentials), so it falls short of explicit routing guidance.

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