mouser-mcp

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Add parts to a Mouser cart

add_to_cart

Adds Mouser parts to a cart, creating a new cart when no cart key is supplied and returning the key; it does not place an order.

Instructions

Adds parts to a Mouser cart. Omit cartKey to start a new cart; the returned cartKey identifies it. Does not place an order.

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": {
      "items": "<items>"
    },
    "name": "add_to_cart"
  }
}

Input Schema

Name	Required	Description	Default
`items`	Yes
`cartKey`	No	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

A4.4/5.0

Behavior4/5

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

Annotations already declare readOnly=false, destructive=false, idempotent=false, and openWorld=true, so the safety profile is covered. The description adds genuinely new behavior: a new cart is created implicitly when cartKey is absent, and the returned cartKey is the handle for that cart. It leaves unstated what happens when the same part is added twice, which matters given idempotentHint=false.

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

Conciseness5/5

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

Three short sentences, each carrying distinct information: what it does, the key parameter rule, and the scope boundary. Nothing is redundant and the essential action is front-loaded.

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?

An output schema exists, so return-value detail is correctly left out, though it still usefully notes the returned cartKey. For a two-parameter mutation tool the coverage is nearly complete; the only meaningful omission is the duplicate-part/quantity-merge behavior implied by idempotentHint=false.

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 only 50%, with mouserPartNumber and quantity undocumented in the schema. The description compensates for the most consequential gap by explaining that cartKey is optional and its omission creates a new cart, a semantic the schema text ('Mouser cart key.') does not convey.

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

Purpose5/5

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

States a specific verb and resource ('Adds parts to a Mouser cart') and immediately bounds the scope with 'Does not place an order.' The verb 'adds' cleanly separates it from sibling tools like update_cart_items, remove_from_cart, and create_cart_from_order.

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

Usage Guidelines4/5

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

Gives a concrete conditional rule: omit cartKey to start a new cart, otherwise pass the existing one. The 'does not place an order' line also tells the agent when this is not sufficient. It stops short of naming alternate siblings for order-based carts (create_cart_from_order), so it is strong but not exhaustive.

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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