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

With no annotations, the description carries the burden of conveying behavior. It discloses that the tool is a read-only-ish lookup returning two pieces of information (in-market status and serving TDU). It does not mention edge cases or error handling, but for a simple single-parameter lookup the behavior is reasonably transparent.

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?

A single sentence that front-loads the essential purpose without any filler. Every word earns its place, and the structure makes the tool's behavior immediately understandable.

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?

Given the tool's simplicity (one parameter, no output schema, no annotations), the description provides enough context for an agent to select and invoke it correctly: input is a zip, output is a yes/no plus TDU. It does not detail the return format or behavior for invalid zips, but the natural-language description is largely 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?

Schema description coverage is 0%, so the description must compensate for the undefined 'zip' parameter. It does reference 'zip' but adds no format details (e.g., 5-digit vs ZIP+4, US-only, valid ranges). The parameter name is intuitive, but the description does not enrich it beyond the schema's string type.

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 check: whether a zip is in the deregulated Texas market and which TDU serves it. This clearly distinguishes it from siblings like compare_plans, compare_this_house, and explain_plan, which address different domains. The resource (zip) and the two-part output are explicit.

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?

The intended usage is implied by the description: an agent would call this when given a zip and needing territory/market eligibility information. However, it does not explicitly state when to use it over the listed sibling tools or provide any exclusions or alternatives. No when-to-use guidance is given beyond the natural purpose.

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