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

Adds context beyond the annotations: the change is applied immediately ('it runs at once') and executed under the identity of 'the person' in Kooga, and an empty value clears the field. The annotations already flag destructiveHint=true and idempotentHint=false; the description's clearing semantics are consistent with destructiveness rather than contradicting it, though it does not spell out the consequence of a null write explicitly enough to fully justify the destructive flag.

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 verb, fields, and the sibling reference in the first clause. The subscription rationale ('a person is subscribed only when they agreed to it themselves...') is slightly ornate relative to the operational point, but it justifies the exclusion rather than wasting space.

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?

With an output schema present, return values need no explanation, and the description covers edit scope, clearing behavior, exclusions, and execution timing. The only mild gap is that it never mentions workspaceId scoping, which matters for multi-workspace connections.

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 only 40%, so the description must compensate, and it does for the three undocumented optional fields by naming them and explaining that an empty value clears them (important given the anyOf null typing). contactId and workspaceId are already documented in the schema, and the description still reinforces contactId's origin from findContacts.

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 plus the exact editable fields (name, city, country) and points at findContacts as the source of the contactId. An agent can distinguish it from readContact (read), findContacts (lookup) and unsubscribeContacts (consent) without opening a 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 explicit scope limits (address and consent cannot be changed here) and names the correct alternative for the adjacent need: 'To stop mailing someone, use unsubscribeContacts.' It also explains the null/empty semantics for the editable fields, so there is no ambiguity about when to call this tool.

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