Trello MCP Server

Get Card Custom Fields

get_card_custom_fields

Fetches custom field values from a Trello card to retrieve structured data stored on that card.

Instructions

Get custom field values for a Trello card. Requires Trello Premium or Enterprise.

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": {
      "cardId": "<cardId>"
    },
    "name": "get_card_custom_fields"
  }
}

Input Schema

Name	Required	Description	Default
`cardId`	Yes	The ID of the card

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.2.0Sep 6, 2026

TDQS

A3.8/5.0

Behavior3/5

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

No annotations are provided, so the description carries the behavioral disclosure burden. It does state that this is a read operation and discloses a meaningful access restriction (Premium/Enterprise), but it does not describe the response shape or behavior for missing/empty custom field values.

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?

Two sentences with no filler. The action and resource are front-loaded, and the Premium requirement is the only additional necessary context. Every word earns its place.

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?

For a low-complexity, one-parameter read-only tool, the description plus schema is largely sufficient: it covers purpose, resource, prerequisite, and required parameter. The only gap is that with no output schema or annotations, a brief note on the return shape would make it fully complete.

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 description coverage is 100%, and the single parameter cardId is already described as 'The ID of the card.' The description adds no new parameter detail beyond the schema, so the baseline score of 3 is appropriate.

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?

The description states a specific verb and resource: 'Get custom field values for a Trello card.' It clearly distinguishes this from sibling tools like get_board_custom_fields by specifying card-level scope, and it matches the tool name and title without ambiguity.

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 description provides an explicit prerequisite ('Requires Trello Premium or Enterprise'), which is useful for deciding whether the tool is available. However, it does not contrast with alternatives such as get_board_custom_fields or get_custom_field, leaving when-to-use versus those siblings only implicit.

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

Deploy Server