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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is fully covered. The description adds one genuine behavioral detail beyond that — that disabled providers are surfaced with enabled=false rather than omitted — but says nothing about pagination, ordering, or account scoping.

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, zero waste, with the primary purpose front-loaded before the secondary return-value note. Nothing could be removed without losing information.

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 parameterless, annotation-covered, closed-world list call with no output schema, the description covers what is enumerated plus the notable enabled=false case. Slightly more detail on the shape of the add-on allowance result would make it fully self-sufficient.

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 no argument meaning for the description to add; the baseline for a parameterless tool is 4. Nothing in the description misleads about inputs.

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?

The description uses a specific verb and resource ('List owned phone numbers') and adds a second payload element ('add-on allowance'), which cleanly separates it from create_phone_number and release_phone_number among the siblings. It stops short of naming an alternative explicitly, but the resource is unambiguous.

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?

Usage is only implied: an agent can infer this is the enumeration call for provisioned numbers, but there is no stated when-to-use versus when-not, and no guidance on pairing it with related tools such as list_sms or release_phone_number.

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