mouser-mcp

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Update items in a Mouser cart

update_cart_items

Idempotent

Change quantities or customer part numbers for parts already in a Mouser cart, enabling corrections to an existing cart without rebuilding it.

Instructions

Changes quantities or customer part numbers of parts already in a Mouser cart.

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": {
      "cartKey": "<cartKey>",
      "items": "<items>"
    },
    "name": "update_cart_items"
  }
}

Input Schema

Name	Required	Description	Default
`items`	Yes
`cartKey`	Yes	Mouser cart key.

Output Schema

Name	Required	Description	Default
`items`	Yes
`cartKey`	No
`currency`	No
`itemCount`	No
`merchandiseTotal`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.0.5Nov 6, 2026

TDQS

B3.4/5.0

Behavior3/5

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

Annotations already declare readOnly=false, idempotent=true, destructive=false and openWorld=true, so safety and idempotency are covered elsewhere. The description's only added signal is the boundary that only quantities and customer part numbers can change (not the part itself). It says nothing about error behavior when a part isn't in the cart, the 100-item cap, or whether unlisted items are preserved.

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

Conciseness4/5

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

A single front-loaded sentence with no filler. Its brevity is close to under-specification rather than verbosity, but nothing in it is wasted.

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

Completeness3/5

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

An output schema exists and annotations carry the safety/idempotency profile, which reduces the burden. Still, for a mutation that takes an arbitrary list of item patches, the description leaves key questions open: are quantities overwritten or added, are unmatched parts rejected, and are omitted cart lines untouched.

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

Parameters3/5

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

Schema coverage is 50%: cartKey and customerPartNumber are documented in the schema, while mouserPartNumber and quantity are not, so the description only partially compensates by linking the two mutable fields to the update. It does not clarify that items must match existing cart lines or how quantities are interpreted (set vs increment).

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 ('changes') and resource ('parts already in a Mouser cart') plus the two mutable fields, which separates it from add_to_cart and remove_from_cart without naming them. It stops short of an explicit sibling comparison, so it lands at clear-but-undifferentiated.

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

Usage Guidelines3/5

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

The phrase 'already in a Mouser cart' implies the precondition for use and indirectly excludes adding/removing, but the description never names add_to_cart, remove_from_cart, or get_cart as alternatives, and gives no when-not-to-use guidance.

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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