TimeLib MCP

update_variant

Update a product variant's title, SKU, prices, inventory management, and options. Specify product and variant IDs to apply changes through the Medusa Admin API.

Instructions

Update a variant (title, sku, prices, manage_inventory, options).

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_id": "<product_id>",
      "variant_id": "<variant_id>"
    },
    "name": "update_variant"
  }
}

Input Schema

Name	Required	Description	Default
`sku`	No
`title`	No
`prices`	No
`product_id`	Yes
`variant_id`	Yes
`manage_inventory`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Aug 4, 2026

TDQS

C2.7/5.0

Behavior2/5

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It implies mutation but doesn't state what happens to unspecified fields (are they preserved or reset?), whether prices requires multiple price objects, whether manage_inventory interacts with inventory levels, or what the response contains. A mutation tool with zero annotation coverage should describe more behavioral detail.

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 efficient sentence lists the resource and updatable fields with no wasted words. It could be argued it's under-specified rather than concise, but for what it includes, it's tight.

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

Completeness2/5

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

For a 6-parameter mutation tool with no annotations and no output schema, this description is too thin. It doesn't explain the prices array structure, the interplay of manage_inventory with inventory tools (set_inventory_level, list_inventory_items are siblings), or what the update response returns. Given the tool is a mutation with side effects, more completeness is warranted.

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

Parameters2/5

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

Schema description coverage is 0%, so the description must compensate. It names title, sku, prices, manage_inventory, and options as updatable fields, providing basic mapping to 5 of 6 parameters. However, it doesn't explain the structure of 'prices' (array of objects with unknown shape), the meaning of manage_inventory, or how 'options' maps. The 'options' field isn't even in the schema, creating confusion about whether it's a valid update field or free-form.

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?

The description states a specific verb ('Update') with a clear resource ('variant') and enumerates the fields it affects: title, sku, prices, manage_inventory, options. This is clear and distinguishes from sibling create_variant and delete_variant, though it doesn't explicitly name these alternatives.

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?

No context is given for when to use this tool vs alternatives. It doesn't clarify that a variant must first exist, whether create_variant is preferred for new variants, or when delete_variant might apply. There is no guidance on when updating fields would require inventory management (manage_inventory) coordination.

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