Rack Warehouse fitment

Check fit

check_fit

Read-only

Whether one product fits one vehicle: 'yes' with the fit options and the price and page for the vehicle, 'not listed', or 'by what it mounts to' for carriers. Also what the product needs (crossbars, a hitch, required parts) and what checkout will ask. The product is its rackwarehouse.com page URL, its handle or its SKU.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "product": "<product>",
      "make": "<make>",
      "model": "<model>"
    },
    "name": "check_fit"
  }
}

Input Schema

Name	Required	Description
`make`	Yes	Make handle or name, e.g. toyota (find_vehicle gives it)
`year`	No	Model year, e.g. 2018
`model`	Yes	Model handle or name, e.g. corolla
`product`	Yes
`roof_type`	No	e.g. Naked Roof, Raised Rails, Flush Rails, Fixed Point, Tracks, Gutter

Schema Changelog

Changes observed during successful MCP inspections.

First observedSep 28, 2026

TDQS

A3.5/5.0

Behavior4/5

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description usefully discloses the response semantics ('yes' with fit options/price/page, 'not listed', 'by what it mounts to') and that it reports required parts and checkout prompts — genuine behavioral context given there is no output schema.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness3/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences, each carrying information, but the first sentence is a dense run-on that nests quoted answer strings and is hard to parse on first read. Purpose is front-loaded, but structure could be cleaner.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description does the necessary work of describing return values and required-parts reporting, and it documents the product parameter. It is largely complete, though it leaves the check_fit vs what_fits boundary ambiguous.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 80%, and the one undocumented parameter (product) is explicitly explained in the description as a page URL, handle, or SKU, compensating for the gap. It adds real meaning beyond the structured fields rather than restating them.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource — whether one product fits one vehicle — and enumerates the possible answers, so an agent knows the operation. It does not differentiate itself from the sibling what_fits, which sounds like an overlapping fit-check, so it falls short of a 5.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no explicit when-to-use guidance and no mention of the alternatives (find_vehicle, what_fits) that an agent must choose between. Usage is only implied by the description of the answer values.

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

All Rack Warehouse fitment tools Inspect

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