Trello MCP Server

add_attachment_url

Attach a file to a Trello card from a URL. Provide the card ID and URL, then optionally set a display name or use the attachment as the card cover.

Instructions

Ajoute un attachment à une carte via URL

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>",
      "url": "<url>"
    },
    "name": "add_attachment_url"
  }
}

Input Schema

Name	Required	Description
`url`	Yes	Parameter url
`name`	No	Parameter name
`cardId`	Yes	Parameter cardId (24 characters)
`setCover`	No	Parameter setCover

Schema Changelog

Changes observed during successful MCP inspections.

First observedv2.1.0Sep 6, 2026

TDQS

B3.2/5.0

Behavior2/5

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

With no annotations, the description carries the full burden of behavioral disclosure. It identifies the mutation ('adds') but does not explain side effects, whether setCover replaces the card cover, URL validity requirements, or any permission constraints.

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, efficient sentence with no filler. The key information—what action, what resource, and by what method—is front-loaded and immediately understandable.

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 mutation tool with four parameters, no annotations, and no output schema, this description is too sparse. It does not explain the optional parameters, the effect of setCover, or any expected response/result, leaving the agent to infer important calling details.

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 reported as 100%, so the baseline is 3. However, the parameter descriptions are largely tautological ('Parameter url'), and the tool description only meaningfully clarifies the url parameter via 'via URL'; name and setCover semantics remain unexplained.

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 action ('Ajoute un attachment'), the target resource ('à une carte'), and the mechanism ('via URL'). This clearly distinguishes it from siblings like list_attachments, delete_attachment, and set_card_cover.

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 guidance is given about when to use this tool versus alternatives, such as set_card_cover or adding a file attachment. The description implies its purpose but offers no context, exclusions, or conditions.

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

Deploy Server