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

Adds real side-effect context beyond the annotations: include_autoresponder is flagged as sending EMAIL to the contact, and remove_from_all_other_lists is described as removing the contact from every list not in add_to_list_ids (with its add_to_list_ids dependency). What's left unsaid is whether omitted `fields` are preserved or cleared by the update_full_contact endpoint — a material ambiguity for a destructiveHint=true mutation.

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-loads the WRITE marker and primary action, then covers each parameter in a single clause with zero filler. Dense but well-ordered, and the endpoint reference sits harmlessly at the end.

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?

For a 6-parameter destructive mutation with no output schema, the definition covers identifying the contact, formatting fields, list add/remove semantics, and the email-triggering side effect. The remaining gap is update semantics (partial vs full replacement) and any indication of the response, which matters given the update_full_contact endpoint name.

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 already 100%, so the baseline is 3; the description earns above that by stating that `fields` keys are user_tags, that the email address cannot be changed via this tool, and by disclosing the cross-parameter constraint that remove_from_all_other_lists requires add_to_list_ids — a rule not encoded in the schema. It does not clarify merge-vs-replace semantics for `fields`.

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?

Opens with a specific verb and resource: "WRITE: change an existing contact's data fields and/or list memberships in one call." It scopes exactly what can be changed (data fields and list memberships) and implicitly contrasts with the narrow siblings robly_add_contact_to_list and robly_remove_contact_from_list by combining both operations.

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?

Explicitly routes the agent to prerequisites: look up member_id with robly_find_contact, get field keys from robly_list_fields, and notes the email cannot be changed here. It never explicitly says when to prefer this over robly_add_contact_to_list / robly_remove_contact_from_list for single-list operations, which keeps it short of a 5.

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