AniList MCP Server

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Post a message activity

post_message_activity

Post a public message-style activity to an AniList user's profile or update an existing one by ID. Note: messages are publicly visible, not private.

Instructions

[Requires login] Post a new message-style activity to another AniList user's profile, or update an existing one by passing its id. Despite the name, this is NOT a private DM — like post_text_activity, it's publicly visible on both users' activity feeds/profiles to anyone who can view them. This is a limitation of this tool, not AniList itself: AniList's underlying mutation does accept a private argument, but this tool doesn't expose it, so every message sent through it is public. Don't use it for anything the sender expects to stay confidential.

Input Schema

TableJSON Schema

Name	Required	Description
`id`	No	Activity ID to update instead of creating a new post.
`message`	Yes	The message text to post (per AniList's own schema: 2-10000 characters).
`recipientId`	Yes	AniList numeric user ID of the message recipient (resolve a username via search_user first).

Output Schema

TableJSON Schema

Name	Required	Description	Default
`activity`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedv0.9.0Sep 27, 2026
- removedOutput schema / properties / activity / properties / message / anyOf
```
Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]
```
- addedOutput schema / properties / activity / properties / message / type
```
Added value: +[
+  "string",
+  "null"
+]
```
Changed8 schema fields changedv0.7.1Aug 1, 2026
- addedInput schema / properties / id / exclusiveMinimum
```
Added value: +0
```
- removedInput schema / properties / id / minimum
```
Removed value: --2147483648
```
- addedInput schema / properties / recipientId / exclusiveMinimum
```
Added value: +0
```
- removedInput schema / properties / recipientId / minimum
```
Removed value: --2147483648
```
- addedOutput schema / properties / activity / properties / id / exclusiveMinimum
```
Added value: +0
```
- changedOutput schema / properties / activity / properties / id / maximum
```
Previous value: -9007199254740991New value: +2147483647
```
- removedOutput schema / properties / activity / properties / id / minimum
```
Removed value: --9007199254740991
```
- changedOutput schema / properties / activity / properties / siteUrl / anyOf
```
Previous value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "format": "uri",
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]
```
Changed3 schema fields changedv0.5.0Jul 29, 2026
- changedInput schema / properties / message / description
```
Previous value: -"The message text to post."New value: +"The message text to post (per AniList's own schema: 2-10000 characters)."
```
- addedInput schema / properties / message / maxLength
```
Added value: +10000
```
- changedInput schema / properties / message / minLength
```
Previous value: -1New value: +2
```
Addedv0.2.0Jul 21, 2026

TDQS

A4.7/5.0

Behavior5/5

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

The description goes well beyond the annotations by revealing that the operation is publicly visible despite the 'message' framing, that the underlying AniList mutation supports a 'private' argument the tool does not expose, and that updates are possible. This directly addresses the most likely misconception about the 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 compact and front-loaded: the main purpose comes first, then the update mode, then the critical visibility warning. Every sentence earns its place and no unnecessary wording is present.

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 mutation tool with a detailed input schema and an output schema, the description provides the essential operational context: login requirement, public visibility, update behavior, and a clear confidentiality warning. Nothing critical is missing for correct invocation.

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% and each parameter already has a clear schema description. The tool description adds context about 'id' meaning update mode, but largely restates what the schema already documents. It does not significantly enhance parameter-level understanding beyond the schema.

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 ('Post a new message-style activity to another AniList user's profile') and a second mode ('or update an existing one by passing its id'). It also differentiates the tool from a private DM and references post_text_activity for comparison, making the tool's identity unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly states the login requirement, distinguishes create-vs-update usage, and gives a clear when-not-to-use rule: do not use it for anything the sender expects to stay confidential. This is strong practical guidance for an agent deciding whether to invoke it.

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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