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

Annotations already declare readOnlyHint=false, destructiveHint=true, and idempotentHint=false. The description adds rich context beyond those: it clarifies that remove_sms_trunk_ids only unlinks (does not delete trunks), that deleting the group requires a different tool which does delete trunks, that only specific trunk types can be added, and that the response is the updated group with members or a readable error.

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 core purpose, then proceeds through partial-update semantics, eligibility constraints, deletion alternative, and return value. Every sentence carries actionable information; no filler or repetition.

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 mutation tool with no output schema and four fully described parameters, the description covers purpose, when to use/avoid, prerequisites, side effects, and return format. Annotations already cover the safety profile, so nothing essential 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 description coverage is 100%, so the baseline is 3. The description adds a meaningful constraint not present in the schema: only inbound-capable HTTP IN, SMTP, SMSC or ESME trunks can be added, and a trunk already in another group must be removed there first. It otherwise largely paraphrases the schema's field descriptions.

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 (update) and resource (SMS trunk group) scoped to the authenticated customer's groups. It distinguishes itself from siblings by naming list_sms_trunks as the id source and delete_sms_trunk as the deletion alternative, so an agent can tell it apart without opening any schema.

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 frames this as a partial update and enumerates the three optional fields. It gives when-not-to-use (deletion via delete_sms_trunk) with a warning, and states prerequisites for adding trunks (only inbound-capable types; trunk must first be removed from any other group). Alternatives and conditions are spelled out rather than inferred.

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