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

With no annotations, the description carries the full behavioral burden. It discloses that the lookup is free, is a 'first look' (implying limited detail), uses the FMCSA QCMobile path, and counts against a trial quota. However, it does not mention error behavior, rate limits, or the exact return structure beyond listing fields. Some context is added, but gaps remain.

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 a single, efficient sentence that front-loads the core purpose ('Free USDOT / DOT carrier first look') and then lists fields and quota impact. It is concise without unnecessary fluff, though it packs several details into one sentence.

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 simple one-parameter lookup with no output schema, the description adequately covers what the tool returns (legal name, allowed-to-operate, fleet, dockets, cargo, authority) and notes the trial quota. It could mention error conditions or what happens on invalid numbers, but these are minor omissions given the simplicity.

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%: the query parameter is fully described with format rules (digits only, optional prefix stripped). The tool description adds no extra meaning beyond that, so the baseline 3 is appropriate since the schema does the heavy lifting.

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 clearly states the tool's function: a USDOT carrier lookup. It specifies the resource (USDOT/DOT number) and the verb ('lookup'), and lists the returned census fields. The title and description together distinguish it from siblings like lookup_mc and lookup_name by the identifier type.

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 implied by the name and description (use when you have a USDOT number), but there is no explicit guidance on when to prefer this over lookup_mc or lookup_name, nor any exclusions. The quota note ('Counts 1 toward the shared 5-lookup MCP trial') provides context on shared limits but doesn't direct tool selection.

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