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

Annotations already flag destructiveHint=true, but the description earns extra credit by explaining exactly what is destroyed: `members` replaces the entire list, unlisted trunks are detached yet survive as standalone trunks, nothing is deleted, and a failed call changes nothing. That is behavioral detail no annotation or schema conveys.

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 purpose and then the critical replacement warning, with the destructive caveat emphasized in caps. Slightly over-explains member fields that the schema already documents, but every sentence still carries useful 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?

With no output schema, the description supplies the return contract ('updated group with its members in routing order, or a readable error'), covers all four parameters, and discloses the atomic failure behavior. Nothing an agent needs to call this safely is missing.

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, but the description adds relational meaning the schema cannot express: replacement semantics for `members`, omit-vs-empty-array behavior, and the routing interpretation of priority (lowest first) and weight (higher preferred among equal priorities).

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+resource ('Update one of the authenticated customer's Voice IN Trunk Groups') and names the updatable fields, clearly separating it from siblings like update_sms_trunk_group or update_trunk_group. It even points at list_trunk_groups as the source of the id.

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 precise conditional guidance: pass fields to change, omit `members` to leave membership untouched, pass an empty array to detach all. It does not explicitly compare against a sibling alternative (e.g., when to use this vs. update_trunk_group), so it falls just short of the top band.

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