List mobile carriers (MNOs)

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

Annotations already indicate readOnlyHint=true, idempotentHint=true, destructiveHint=false, so the description's behavioral disclosure is minimal. It adds domain relevance (10DLC) but does not describe additional behaviors like rate limits or side effects.

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 concise sentences, front-loaded with the action. No wasted words.

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?

Low complexity tool (no parameters, no output schema). Description fully explains the tool's purpose (list MNOs for 10DLC) and links to related tool msg_get_mno_status. Complete for its scope.

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?

No parameters; baseline 4 applies. Schema coverage is 100% (trivially). Description adds no param info, which is fine since none exist.

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?

Description clearly states it lists MNOs relevant to 10DLC registration, with examples (AT&T, T-Mobile, Verizon). It distinguishes from sibling msg_get_mno_status by noting it's reference data for interpreting that tool's results.

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?

States the tool provides reference data for interpreting msg_get_mno_status results, giving clear context. Does not explicitly exclude other uses or mention when not to use, but the context is sufficient for this simple tool.

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