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

With no annotations, the description carries the full burden. It discloses that the tool is 'Free' and that it 'Counts 1 toward the shared 5-lookup MCP trial', which is important for quota management. It also implies a limited 'first look' behavior. However, it does not clarify whether the operation is read-only, what happens on invalid input, or the exact nature of the returned data. The quota disclosure adds value, but other behavioral aspects are left unspecified.

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?

The description is three concise sentences with no redundant phrasing. The main purpose is front-loaded in the first sentence, input format is in the second, and quota impact in the third. Each sentence earns its place, and the overall length is appropriate for a simple lookup tool.

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?

The tool has no output schema, so the description should clarify what the agent can expect as a return. 'Carrier first look' suggests a preview of carrier information, but it does not explicitly state the return format or content. The quota information is useful, but for a lookup tool with one parameter, a bit more detail about the output would improve completeness. Given the simplicity, the description is adequate but not fully 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 description coverage is 100%, with the parameter 'query' documented as 'Docket number with MC, MX, or FF prefix (e.g. MC-123456)'. The description's mention of 'Accepts MC-123456 or prefixed docket input' essentially repeats this information, adding no new semantic detail. The baseline of 3 applies because the schema already covers the parameter.

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 states a specific action ('carrier first look') and resource ('MC, MX, or FF docket'), clearly distinguishing this from sibling tools lookup_dot and lookup_name which likely handle DOT numbers and carrier names. The title and name reinforce this, making the purpose 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?

The description provides no explicit guidance on when to use this tool versus lookup_dot or lookup_name. The only contextual hint is the mention of 'same path as verifreta.com/tools/mc-number-lookup', which is an external URL and not useful for an agent. No exclusions or alternative routing are given.

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