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

The description goes well beyond the annotations. It discloses the required permission, details the partial-update (idempotent) behavior, explains variable-name resolution and failure with 422 before writing, states that variable writes propagate to the live bot immediately, and describes the side effect of setting status to 'unsubscribed' (stops broadcasts and sequences). This is rich, actionable behavioral 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 five sentences, each serving a distinct purpose: main action, permission, idempotency, variable semantics, and side-effects. It is front-loaded with the core purpose and contains no filler or redundant phrasing.

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 having no output schema, the description covers all critical operational aspects: permission requirements, partial update semantics, error behavior, propagation timing, and side effects on broadcasts/sequences. Given the tool's complexity (9 parameters, nested object, enums), this level of detail is excellent and leaves no major gaps.

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 the baseline is 3. The description adds extra meaning beyond the schema by explaining that the variables map takes names (or folder paths) and that unknown names fail with 422 before any write. It also clarifies the partial-update semantics for all fields, which is not fully captured in the schema's 'Omit to leave unchanged' notes. This pushes it above baseline.

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+resource: "Update a contact's profile fields and/or contact-variable values." This clearly distinguishes the tool from siblings like create_contact, get_contact, and list_contacts by conveying that it modifies existing contacts and their variables.

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 provides clear context for when to use the tool: it requires the manage_broadcasts permission, and it explains partial-update semantics. It does not explicitly name alternatives or warn against using it for creation, but the sibling list and the verb 'update' make the use case unambiguous. The omission of explicit exclusion is a minor gap.

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