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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds real value: the full set of status values, the per-number billing formula (monthly_price × DID count, setup_price one-time, USD), and the last-verification status enum. It doesn't mention rate limits or pagination defaults (those live in schema).

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?

Purpose is front-loaded in the first sentence, followed by a dense field enumeration and a useful billing sentence. The long return-field list is heavy but earns its place given there is no output schema. Minor verbosity, but no waste.

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 present, the description compensates by enumerating the returned fields and statuses, and explains billing so the agent can interpret costs. Combined with annotations covering the safety profile, an agent has everything needed to call and interpret this tool.

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% for both page and page_size, so the schema fully documents pagination. The description only notes 'plus pagination meta' without adding syntax or constraint detail beyond the schema, so the baseline 3 applies.

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 ('List the authenticated customer's Emergency Calling Services') with clear scope (authenticated customer). Easily distinguished from siblings like list_emergency_requirements or create_emergency_verification.

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 routes the agent to create_emergency_verification for services in 'changes required' status. It also clarifies billing semantics, giving useful context. However, it does not state when not to use this tool versus list_emergency_requirements, so it stops short of the 5 bar.

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