check_carrier_listChecks up to 25 U.S. carriers or brokers at once (USDOT numbers; MC numbers also accepted, up to 10) and returns each one's most important red flag from FMCSA public records, urgent ones first. Use to screen a carrier list or a load board shortlist.
| Name | Required | Description | Default |
|---|---|---|---|
| numbers | Yes | USDOT or MC numbers |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description still adds real value beyond them: it discloses the return contract ('each one's most important red flag ... urgent ones first') and a hidden input constraint ('MC numbers also accepted, up to 10') not present in the schema. No contradictions with annotations.
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, front-loaded with the batch capability and limits, then the use case. Every clause carries information (count, identifier type, per-type cap, data source, return ordering) with no filler.
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?
No output schema exists, so the description must carry the return contract, and it does describe what comes back (the single most important red flag per carrier, urgent first). It stops short of describing per-carrier output shape or behavior on invalid/unknown numbers, which leaves a small gap for a screening tool.
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?
With one parameter at 100% schema coverage, the baseline is 3, but the description genuinely adds meaning the schema lacks: MC numbers are accepted but capped at 10 while USDOT supports the full 25. The schema description ('USDOT or MC numbers') conveys none of that nuance.
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 verb and resource ('Checks ... U.S. carriers or brokers') with precise batch scope ('up to 25 ... at once') and the source of truth (FMCSA public records). It implicitly separates itself from the singular sibling lookup_carrier via 'at once,' but never names the alternative, so differentiation is inferred rather than stated.
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?
Gives a clear triggering context: 'Use to screen a carrier list or a load board shortlist.' That tells the agent when to reach for this tool. However, it offers no exclusions or explicit routing (e.g. 'for a single carrier use lookup_carrier'), so the agent must infer the boundary with siblings.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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