Trello MCP Server

Create Custom Field

create_custom_field

Add custom fields (checkbox, date, list, number, text) to a Trello board to capture tailored data. Requires Trello Premium or Enterprise.

Instructions

Create a new custom field definition on a board. 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": {
      "idModel": "<idModel>",
      "name": "<name>",
      "type": "<type>"
    },
    "name": "create_custom_field"
  }
}

Input Schema

Name	Required	Description
`pos`	No	Position of the field
`name`	Yes	Name of the custom field
`type`	Yes	Type of the custom field
`idModel`	Yes	The ID of the board

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.2.0Sep 6, 2026

TDQS

A3.5/5.0

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 mentions the Premium/Enterprise requirement but does not disclose what happens on success, whether the operation is reversible, what permissions are needed beyond the plan, or any side effects on the board and its cards. This is a significant gap for a mutation tool.

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?

The description is a single, front-loaded sentence with no wasted words. It states the core action and the key requirement, earning every word.

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?

The description is adequate for a simple create tool given 100% schema coverage, but it lacks behavioral context such as return value, error conditions, or relationship to other custom-field operations. It meets the minimum viable threshold but has clear gaps.

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 100%, so the schema already documents all four parameters clearly. The description adds no parameter-level meaning, which is acceptable because the schema covers meaning fully. Baseline 3 applies.

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 uses a specific verb ('Create') and a specific resource ('custom field definition on a board'), clearly distinguishing this tool from siblings such as get_custom_field, update_custom_field_item, and delete_custom_field. The scope is explicit and leaves no ambiguity about what the tool does.

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 statement 'Requires Trello Premium or Enterprise' provides a prerequisite but no guidance on when to use this tool versus alternatives. The action phrase 'Create a new custom field definition' implies the use case, but there are no explicit when/when-not conditions or references to related tools like get_board_custom_fields or update_custom_field_item.

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

Deploy Server