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List attachments

list_attachments

Read-onlyIdempotent

List files attached to a work package, wiki page, meeting, document, budget, or comment to discover attachment IDs before downloading or check what a container already contains.

Instructions

List the files attached to one container.

Containers are work packages, wiki pages, meetings, documents, budgets and comments. Use this to discover attachment ids before calling download_attachment, or to check what a work package already carries. The upstream collection is not paginated, so it is fetched in full: the envelope always reports has_more=false and a total equal to the row count.

Returns the standard list envelope; each row has id, file_name, size_bytes, content_type, description, author, created_at and status. status is the virus-scan state — 'uploaded' and 'scanned' are downloadable, 'quarantined' files are not, and anything else is still being scanned and is readable only by its uploader.

Pitfalls: container_id identifies the container, not the file. A 404 means the container does not exist or the module providing it (meetings, budgets, documents) is not enabled on this instance. Forum posts are a valid API container but have no discovery path here.

Related: download_attachment fetches the bytes for one row, upload_attachment adds a file to the same containers, and get_work_package(include=['attachments']) returns these rows inline for a single work package.

Input Schema

Name	Required	Description	Default
`container_id`	Yes	Numeric id of the container itself: the work package id, wiki page id, meeting id, document id, budget id, or activity id. Never an attachment id.
`container_type`	Yes	Kind of object that owns the files. Use 'comment' for files attached to a work-package comment — those live on the activity, so pass the activity id from list_work_package_comments as container_id.

Output Schema

Name	Required	Description	Default
`sums`	No
`items`	No
`notes`	No
`groups`	No
`pagination`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed45 schema fields changedv0.4.0Oct 24, 2026

changedOutput schema / properties / groups / anyOf

Previous value: -[
-  {
-    "items": {
-      "description": "A server-side group bucket, computed over the full filtered set.",
-      "properties": {
-        "count": {
-          "default": 0,
-          "description": "Records in this group across all pages.",
-          "type": "integer"
-        },
-        "sums": {
-          "anyOf": [
-            {
-              "additionalProperties": {
-                "type": "number"
-              },
-              "type": "object"
-            },
-            {
-              "type": "null"
-            }
-          ],
-          "default": null,
-          "description": "Per-group sums when show_sums was requested."
-        },
-        "value": {
-          "anyOf": [
-            {
-              "type": "string"
-            },
-            {
-              "type": "null"
-            }
-          ],
-          "default": null,
-          "description": "Group value, e.g. a status name."
-        }
-      },
-      "type": "object"
-    },
-    "type": "array"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "items": {
+      "properties": {
+        "count": {
+          "type": "integer"
+        },
+        "sums": {
+          "anyOf": [
+            {
+              "additionalProperties": {
+                "type": "number"
+              },
+              "type": "object"
+            },
+            {
+              "type": "null"
+            }
+          ]
+        },
+        "value": {
+          "type": [
+            "string",
+            "null"
+          ]
+        }
+      },
+      "type": "object"
+    },
+    "type": "array"
+  },
+  {
+    "type": "null"
+  }
+]

removedOutput schema / properties / groups / default
```
Removed value: -null
```

removedOutput schema / properties / groups / description

Removed value: -"Present only when group_by was requested."

removedOutput schema / properties / items / description
```
Removed value: -"The page of results."
```
removedOutput schema / properties / items / items / description
```
Removed value: -"One attached file."
```

changedOutput schema / properties / items / items / properties / author / anyOf

Previous value: -[
-  {
-    "additionalProperties": false,
-    "description": "A reference to another resource. Canonical output shape.",
-    "properties": {
-      "id": {
-        "anyOf": [
-          {
-            "type": "integer"
-          },
-          {
-            "type": "string"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "default": null,
-        "description": "Resource id."
-      },
-      "name": {
-        "anyOf": [
-          {
-            "type": "string"
-          },
-          {
-            "type": "null"
-          }
-        ],
-        "default": null,
-        "description": "Human-readable name."
-      }
-    },
-    "type": "object"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "properties": {
+      "id": {
+        "type": [
+          "integer",
+          "string",
+          "null"
+        ]
+      },
+      "name": {
+        "type": [
+          "string",
+          "null"
+        ]
+      }
+    },
+    "type": "object"
+  },
+  {
+    "type": "null"
+  }
+]

removedOutput schema / properties / items / items / properties / author / default
```
Removed value: -null
```
removedOutput schema / properties / items / items / properties / author / description
```
Removed value: -"User who uploaded the file."
```

removedOutput schema / properties / items / items / properties / content_type / anyOf

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

removedOutput schema / properties / items / items / properties / content_type / default
```
Removed value: -null
```
removedOutput schema / properties / items / items / properties / content_type / description
```
Removed value: -"MIME type detected by OpenProject from the bytes."
```
addedOutput schema / properties / items / items / properties / content_type / type
```
Added value: +[
+  "string",
+  "null"
+]
```

removedOutput schema / properties / items / items / properties / created_at / anyOf

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

removedOutput schema / properties / items / items / properties / created_at / default
```
Removed value: -null
```
removedOutput schema / properties / items / items / properties / created_at / description
```
Removed value: -"ISO 8601 UTC upload timestamp."
```
addedOutput schema / properties / items / items / properties / created_at / type
```
Added value: +[
+  "string",
+  "null"
+]
```

removedOutput schema / properties / items / items / properties / description / anyOf

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

removedOutput schema / properties / items / items / properties / description / default
```
Removed value: -null
```
removedOutput schema / properties / items / items / properties / description / description
```
Removed value: -"Caption stored with the file."
```
addedOutput schema / properties / items / items / properties / description / type
```
Added value: +[
+  "string",
+  "null"
+]
```

removedOutput schema / properties / items / items / properties / file_name / anyOf

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

removedOutput schema / properties / items / items / properties / file_name / default
```
Removed value: -null
```
removedOutput schema / properties / items / items / properties / file_name / description
```
Removed value: -"Stored file name including extension."
```
addedOutput schema / properties / items / items / properties / file_name / type
```
Added value: +[
+  "string",
+  "null"
+]
```

removedOutput schema / properties / items / items / properties / id / anyOf

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

removedOutput schema / properties / items / items / properties / id / default
```
Removed value: -null
```
removedOutput schema / properties / items / items / properties / id / description
```
Removed value: -"Attachment id; pass it to download_attachment."
```
addedOutput schema / properties / items / items / properties / id / type
```
Added value: +[
+  "integer",
+  "string",
+  "null"
+]
```

removedOutput schema / properties / items / items / properties / size_bytes / anyOf

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

removedOutput schema / properties / items / items / properties / size_bytes / default
```
Removed value: -null
```
removedOutput schema / properties / items / items / properties / size_bytes / description
```
Removed value: -"File size in bytes."
```
addedOutput schema / properties / items / items / properties / size_bytes / type
```
Added value: +[
+  "integer",
+  "null"
+]
```

removedOutput schema / properties / items / items / properties / status / anyOf

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

removedOutput schema / properties / items / items / properties / status / default
```
Removed value: -null
```

removedOutput schema / properties / items / items / properties / status / description

Removed value: -"Virus-scan state: 'uploaded'/'scanned' are downloadable, 'quarantined' is not, anything else is still being scanned."

addedOutput schema / properties / items / items / properties / status / type
```
Added value: +[
+  "string",
+  "null"
+]
```
removedOutput schema / properties / notes / default
```
Removed value: -null
```

removedOutput schema / properties / notes / description

Removed value: -"Degradation markers: capped aggregations, unavailable modules, …"

removedOutput schema / properties / pagination / description
```
Removed value: -"Total/page/page_size/has_more."
```
removedOutput schema / properties / pagination / properties / has_more / description
```
Removed value: -"True when further pages exist."
```
removedOutput schema / properties / pagination / properties / page / description
```
Removed value: -"1-based page number of this result."
```
removedOutput schema / properties / pagination / properties / page_size / description
```
Removed value: -"Records requested per page."
```
removedOutput schema / properties / pagination / properties / total / description
```
Removed value: -"Total matching records on the server."
```
removedOutput schema / properties / sums / default
```
Removed value: -null
```

removedOutput schema / properties / sums / description

Removed value: -"Present only when show_sums was requested."

First observedv0.1.0Aug 12, 2026

TDQS

A4.8/5.0

Behavior5/5

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

With annotations already covering read-only, idempotent and non-destructive, the description goes further: it discloses that the upstream collection is unpaginated so has_more is always false and total equals row count. It also explains the virus-scan status vocabulary and which values are downloadable, plus what a 404 means.

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 purpose, then return shape, then pitfalls, then related tools — a sensible order with no filler sentences. It is on the long side and repeats a little of the schema's comment/activity-id note, which keeps it from a 5.

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 filtered-list tool it covers calling context (enabled modules, forum-post gap), return semantics (envelope, row fields, status meanings) and adjacent tools. Even though an output schema exists, the extra explanations fill in the gaps an agent would otherwise have to discover at runtime.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is already 100%, and the description still adds value by emphasizing that container_id is the container and never an attachment id, and by listing which modules (meetings, budgets, documents) can cause a 404. Some of the comment/activity-id guidance duplicates the schema, so it is a notch below fully additive.

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 ('List the files attached to one container') and immediately enumerates what a container is. It also contrasts itself with siblings (download_attachment, upload_attachment, get_work_package(include=['attachments'])), so an agent can place it precisely in the tool family.

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?

Gives explicit when-to-use: discover attachment ids before calling download_attachment, or check what a work package already carries. The Related section names alternatives and what each does differently, leaving little to inference.

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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