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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new context: no authentication key is required and no outbound provider call is triggered, which tells the agent this is a static metadata read.

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 with zero waste. The public/zero-cost precondition is front-loaded before the content enumeration and the negative guarantee.

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 parameters, no output schema, and simple read-only annotations, the definition is nearly complete: it lists what categories of information come back. It stops short of describing the response shape, but that is a minor gap for a static discovery endpoint.

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?

The tool takes zero parameters, so there is nothing to document and the baseline applies. The description correctly implies a parameterless call but adds no parameter-level meaning because none exists.

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 (discover) and enumerates the resource contents: voice and carrier integrations, setup boundaries, platform pricing, and documentation. It is clearly distinct from siblings like list_provider_credentials or list_tts_voices, though it never names those alternatives explicitly.

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?

'Public, no key' establishes a precondition, and 'No provider request or call is made' rules out one misreading, but there is no explicit when-to-use guidance versus sibling discovery tools such as list_provider_credentials or get_billing_policy. Usage context is implied (pre-setup discovery) rather than stated.

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