discord-mcp

discord_download_attachment

Downloads a Discord message attachment to the local download folder using channel, message, and attachment IDs, returning the saved file path, size, content type, and SHA-256 hash.

Instructions

Download a message attachment from Discord into the local download folder (DISCORD_MCP_DOWNLOAD_DIR, default ~/Downloads/discord-mcp). Requires the message ID and the specific attachment ID (attachment_id comes from the attachments of discord_get_message). Returns local file path, size, content type and SHA-256 hash. Bot permissions it may need: View Channel, Read Message History. Writes a file to the local download folder and changes nothing in Discord.

Input Schema

Name	Required	Description
`channel_id`	Yes	ID of the channel or thread that holds the message
`message_id`	Yes	ID of the message
`attachment_id`	Yes	ID of the attachment to download (from the attachments array of discord_get_message)

Output Schema

Name	Required	Description
`path`	Yes
`size`	Yes
`sha256`	Yes
`filename`	Yes
`content_type`	Yes
`attachment_id`	Yes	Discord snowflake ID as a numeric string

Schema Changelog

Changes observed during successful MCP inspections.

Changed6 schema fields changedv0.1.2Nov 4, 2026

addedInput schema / properties / attachment_id / description

Added value: +"ID of the attachment to download (from the attachments array of discord_get_message)"

addedInput schema / properties / channel_id / description

Added value: +"ID of the channel or thread that holds the message"

addedInput schema / properties / message_id / description
```
Added value: +"ID of the message"
```
addedOutput schema / properties / attachment_id / description
```
Added value: +"Discord snowflake ID as a numeric string"
```

removedOutput schema / properties / content_type / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / content_type / type
```
Added value: +[
+  "string",
+  "null"
+]
```

First observedv0.1.0Nov 3, 2026

TDQS

A4.4/5.0

Behavior5/5

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

Adds substantial context beyond the annotations: it names the concrete local write location and the DISCORD_MCP_DOWNLOAD_DIR override, lists the required bot permissions (View Channel, Read Message History), and explicitly reconciles the local file write with the fact that nothing changes in Discord — which explains why readOnlyHint is false despite the operation being non-mutating remotely.

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?

Front-loaded with the action and destination, then prerequisites, then return values and permissions. Every sentence carries information, though the permission sentence is hedged with 'may need', which slightly weakens an otherwise tight structure.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a three-parameter download tool with an output schema already present, the description covers location, prerequisites, permissions, and side effects without redundantly re-explaining the return shape. An agent has everything needed to invoke it correctly and predict the outcome.

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%, so all three parameters are already documented, and the description's note that attachment_id comes from discord_get_message merely restates the schema text. It adds no new format or constraint detail beyond the structured fields, so the baseline of 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?

States a specific verb and resource: 'Download a message attachment from Discord into the local download folder.' It also disambiguates from siblings by naming discord_get_message as the source of the attachment_id, so an agent can distinguish this from get_message or list_messages without reading schemas.

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 clear prerequisite chain: you need channel_id, message_id, and an attachment_id obtained from discord_get_message's attachments. It does not explicitly state when NOT to use this (e.g., for non-attachment content or when the file already exists locally), so it stops short of full routing guidance.

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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