trello-guardrails-mcp

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Add Label

add_label

Add an existing label to a Trello card by specifying board, card, and label names. Uses exact name matching to avoid ambiguity.

Instructions

Add an existing label to a card by label name.

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": {
      "board_name": "<board_name>",
      "card_name": "<card_name>",
      "label_name": "<label_name>"
    },
    "name": "add_label"
  }
}

Input Schema

Name	Required	Description	Default
`card_name`	Yes
`board_name`	Yes
`label_name`	Yes

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 25, 2026

TDQS

C2.9/5.0

Behavior2/5

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

No annotations are provided, so the description must disclose behavioral traits. It only states the action without mentioning side effects (e.g., whether the label is added to the card's label list, whether it overwrites existing labels, idempotency, or permission requirements). The mutation nature is implied but not elaborated.

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?

The description is a single, efficient sentence with no wasted words. It front-loads the action and resource. However, it is so brief that it sacrifices necessary detail, though conciseness itself is well-executed.

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?

With no annotations, 0% parameter coverage, and no mention of return values or error conditions, the description is incomplete for a mutation tool. It does not explain what happens if the label does not exist, whether the operation is idempotent, or what the output schema contains. The agent lacks sufficient context for correct invocation.

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 clarifies that label_name is used by name, but board_name and card_name are not explained beyond their names. No format, constraints, or relationships between parameters are provided, leaving the agent to guess.

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 ('Add'), a resource ('label to a card'), and a key constraint ('existing label' and 'by label name'). This clearly distinguishes it from create_label and other card-related tools. The purpose is unambiguous.

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?

The description implies the label must already exist but does not explicitly state when to use this tool versus create_label, nor does it mention prerequisites like ensuring the label exists on the board. No alternative tools are referenced, leaving the agent to infer usage context.

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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