update_contact

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

Annotations already declare readOnlyHint=false, idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely non-structured information: that this is a partial update ('Only the fields given are changed'), which tells the agent that omitted fields are preserved rather than nulled — a critical behavioral trait for a mutation tool.

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?

Two short sentences, zero filler, with the partial-update guarantee placed immediately after the action statement. Nothing could be removed without losing information.

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 not be explained. However, for a 7-parameter mutation tool the description omits half the editable fields and says nothing about permission requirements or side effects such as a password change affecting the customer-area login.

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 low (14%), so the description is expected to compensate, and it names only three of seven parameters (address, phone, password). The remaining fields (city, postal, country) are undocumented in the description and only partially in the schema, though the contact/country/password/phone schema notes do carry format details.

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?

Specific verb+resource ('Update a contact's ...') with an enumeration of updatable fields, which distinguishes it from create_contact/get_contact in the sibling list. The field list is however partial — the schema also accepts city, postal and country, which the description never mentions, so the stated scope is narrower than the actual one.

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?

There is no statement of when to use this tool versus list_contacts, get_contact or create_contact; the agent must infer that this is the mutation counterpart of get_contact. No prerequisites (e.g. needing a valid contact ID from list_contacts) are given in the description, although the schema notes the ID source.

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