Preview an on-net transfer

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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false. Description adds that BAN is masked and lists ineligibility reasons, which enhances understanding of output behavior.

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 sentences plus a list of reasons and errors. Every sentence adds value, no fluff. Front-loaded with purpose, then usage, then error codes.

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?

Tool has 1 parameter and no output schema. Description explains input format, output behavior (eligibility report with reasons), and possible errors. Combined with annotations covering safety, it's complete.

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% with description for 'tns' parameter. Description says 'Free-form list of 10-digit telephone numbers to check' which mirrors schema but doesn't add new syntax or format details beyond what schema provides.

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 'report which numbers are on-net and eligible for on-net transfer.' Clearly specifies verb (report), resource (TN list), and scope (eligibility for on-net transfer). Differentiates from sibling port_preview (off-net).

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 says 'Use before port_execute_transfer; for off-net numbers use port_preview instead.' Provides clear when-to-use and alternative.

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