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

Annotations already flag destructiveHint=true and idempotentHint=true, but the description adds real value by explaining the destructive mechanism: members is a full replacement and 'omitted members are removed'. It also labels the operation WRITE and gives the PUT semantics, which clarifies the idempotent behavior. It stops short of covering authorization or rate-limit behavior.

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?

A single dense sentence with the most important constraint (full-list replacement/destructive removal) front-loaded right after the WRITE label, plus the endpoint for reference. No filler.

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 4-parameter mutation tool with no output schema, the description covers the key risk (member removal), the replacement contract, and the transport endpoint, and the annotations carry the safety profile. Return-value behavior is undescribed, but with no output schema that is a minor omission.

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 75% (members, group_id, and customer_id carry descriptions, only name is bare), so the schema already does most of the work and the baseline is 3. The description's 'send the FULL list' adds a replacement-semantics nuance the schema doesn't state, but offers nothing new for name, group_id, or customer_id.

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 (rename/replace) plus the resource (contact group) and even the underlying endpoint PUT /contactgroups/{id}. It clearly distinguishes itself from the sibling create_contact_group, delete_contact_group, and list_contact_groups 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?

Usage is implied: use it to change an existing group rather than create or delete one, and the 'and/or' phrasing signals both fields are optional modifications. However, it never explicitly names an alternative tool or states when-not-to-use conditions, so the agent must infer routing from the sibling names.

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