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Trello MCP

Trello MCP

by brainquiver
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
Local

Add Label to Card

add_label_to_card

Assign a single label to a specified Trello card while preserving all existing card labels; obtain the label ID from the board's label list first when unknown.

Instructions

Add one label to a card. The labels already on the card stay. Get label IDs from get_board_labels.

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>",
      "labelId": "<labelId>"
    },
    "name": "add_label_to_card"
  }
}

Input Schema

NameRequiredDescriptionDefault
cardIdYesID of the card
labelIdYesID of the label to add

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.0.0

TDQS

A4/5.0
Behavior3/5

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

With no annotations, the description carries the full burden, and it does disclose the important additive semantics ('labels already on the card stay'). However it is silent on idempotency (re-adding an existing label), required permissions, and failure behavior — meaningful gaps 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?

Three short sentences, front-loaded with the action and the key behavioral fact, zero filler. Every sentence 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 two-parameter mutation tool with no output schema or annotations, the description covers purpose, additive behavior, and the ID prerequisite — enough to invoke it correctly. Duplicate-handling and permission context are the only missing pieces.

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% for both params, so baseline is 3. The description adds only the provenance of labelId (fetch it from get_board_labels) and nothing about cardId or ID formats.

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 ('Add') plus resource ('label') plus scope ('one label to a card'), which cleanly separates it from create_label, and remove_label_from_card. The explicit 'The labels already on the card stay' also distinguishes it from any bulk or replace-style sibling.

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 prerequisite and routes the agent to the sibling 'get_board_labels' to obtain labelId, which is real usage guidance. It stops short of stating when not to use it or what happens if the label is already present, so it doesn't reach a 5.

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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