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Get Direct S3 Upload URL

autoposter_get_media_upload_url

Only for clients that can perform an HTTP PUT or multipart POST (not chat-only clients such as Gemini): if you cannot make that request yourself, use autoposter_create_upload_link instead. Generates a presigned S3 upload URL for direct, high-speed upload of videos or images up to 5GB without size limits or timeouts. Returns direct PUT url, POST upload fields, and public CDN URL.

Input Schema

NameRequiredDescriptionDefault
fileNameYesName of the file including extension (e.g. 'promo_video.mp4', 'photo.jpg').
contentTypeYesMIME type of the media (e.g. 'video/mp4', 'image/jpeg', 'image/png').

Output Schema

NameRequiredDescriptionDefault
keyYesS3 object key for the media file.
cdnUrlYesPublic CDN URL after upload.
successYesWhether the upload URL was successfully created.
uploadPostNoPresigned POST fields if using multipart upload.
directPutUrlYesPresigned S3 PUT URL for direct upload.
instructionsNoInstructions for completing the direct upload.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
+  "properties": {
+    "cdnUrl": {
+      "description": "Public CDN URL after upload.",
+      "type": "string"
+    },
+    "directPutUrl": {
+      "description": "Presigned S3 PUT URL for direct upload.",
+      "type": "string"
+    },
+    "instructions": {
+      "description": "Instructions for completing the direct upload.",
+      "type": "string"
+    },
+    "key": {
+      "description": "S3 object key for the media file.",
+      "type": "string"
+    },
+    "success": {
+      "description": "Whether the upload URL was successfully created.",
+      "type": "boolean"
+    },
+    "uploadPost": {
+      "description": "Presigned POST fields if using multipart upload.",
+      "type": "object"
+    }
+  },
+  "required": [
+    "success",
+    "key",
+    "cdnUrl",
+    "directPutUrl"
+  ],
+  "type": "object"
+}
  2. First observed

TDQS

A4.3/5.0
Behavior4/5

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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds genuine operational context the annotations cannot: a 5GB ceiling, no server-side size limits or timeouts, and the shape of what comes back (PUT url, POST upload fields, public CDN URL). It does not mention auth/credential requirements for the presigned URL, which would be the next useful detail.

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?

A single dense sentence, but it is correctly front-loaded: the disqualifying precondition and the alternative come before the output details, which is exactly the order an agent needs for routing. The trailing enumeration of return values is slightly list-like but each item earns its place.

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

Completeness4/5

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

With an output schema present, the description need not explain returns, and it still summarises them. Combined with the routing precondition and size/timeout characteristics, an agent has enough to select and invoke correctly. Only the credential/auth expectation for the presigned URL is left implicit.

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% with only fileName and contentType, both fully documented in the schema with examples. The description adds no parameter-level detail beyond the tool's general purpose, so the baseline 3 is appropriate when the schema does the heavy lifting.

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: 'Generates a presigned S3 upload URL for direct, high-speed upload of videos or images'. It also names the sibling it is not (autoposter_create_upload_link), so the agent can distinguish the two upload paths without opening either schema.

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 first clause is an explicit precondition: only for clients that can perform an HTTP PUT or multipart POST, not chat-only clients such as Gemini. It names the alternative tool and the exact condition that selects it, which is about as clear as routing guidance gets.

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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