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

Annotations flag this as destructive/non-idempotent, and the description goes well beyond them: it discloses the 10-member cap, the no-nested-group rule, and the important side effect that a member already in another group is moved. It also states atomicity ('nothing is created' on invalid config), which is exactly the kind of behavior an agent needs before calling a mutating 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?

Single dense paragraph that is well front-loaded with the action and resource. Every clause carries information (routing rule, member rules, constraints, return/error behavior), though the block is long enough that an agent must parse carefully.

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 correctly states the return value (created group with members in routing order) and the failure mode (readable error, nothing created). Constraints on members and routing are fully covered, so nothing material is missing for correct invocation.

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 real meaning: it explains the routing semantics of priority (lowest tried first) and weight (higher preferred among equal priorities, which together imply failover vs. load-balancing intent), plus the source of trunk_id values. It does not cover capacity_limit, which is left to the schema.

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 ('Create a Voice IN Trunk Group') and immediately defines it as a failover/load-balancing container of existing trunks, including the routing rule. This clearly distinguishes it from siblings like create_sip_trunk, create_sms_trunk_group, or create_capacity_group.

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 clear operational context: pass `members` to add existing trunks by id from list_trunks, with the explicit constraint that a group cannot contain another group and holds at most 10 members. It names no exclusion against sibling tools (e.g., when to prefer create_sms_trunk_group), so it stops short of 5.

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