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

Annotations already carry the safety profile (readOnlyHint, idempotentHint, destructiveHint, openWorldHint), so the description's burden is lower. The 'Business plan' note adds a plan-availability constraint not present in annotations, which is useful. But it doesn't elaborate what that qualification means or what the shapes of returned entities are.

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, front-loaded with the resource. 'Business plan.' as a bare fragment is terse to the point of ambiguity but does convey a constraint efficiently.

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 zero-param read-only list tool with annotations covering behavior, the description is nearly sufficient. The main gap is the unexplained 'Business plan' qualifier and the lack of any distinction from sibling listing tools (list_did_numbers, list_phone_system), which leaves the agent guessing which to call.

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?

Zero parameters, so the baseline is 4. There are no parameters to describe, and the schema is closed (additionalProperties false). No further parameter context is needed.

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 resource: shared numbers and phone menus on the account. The verb 'Returns' is a bit weak, and it doesn't distinguish itself from siblings like list_did_numbers or list_phone_system, but an agent can identify the resource clearly.

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?

No when-to-use guidance, no alternatives named, no exclusions. The phrase 'Business plan' hints at a prerequisite but is terse and unexplained — it's unclear whether it means the feature is only available on Business plan, or only queries Business-plan accounts. No routing to sibling tools is provided.

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