WebRun Browser Automation

Send task to session

send_task

Destructive

Send a new task to an existing browser session (from create_session). The real Chrome browser may navigate, fill forms, and submit data on third-party websites as the task requires.

Input Schema

TableJSON Schema

Name	Required	Description
`files`	No	Optional file IDs to attach: ids returned by POST /files/upload, or any file already in one of the user's environment catalogs (GET /environments/:id/files). Max 5 files.
`prompt`	Yes	Task description
`secrets`	No	Domain-matched secrets [{match, fields}] (not stored)
`webhook`	No	Webhook configuration
`sessionId`	Yes	Session ID from create_session
`outputType`	No	Response format
`maxDuration`	No	Max duration for this task in minutes (3-60). Defaults to the value the session was created with.
`startingUrl`	No	URL to navigate to before starting this task (optional)
`outputSchema`	No	JSON Schema for structured output (required if outputType is structured_json)
`maxInputTokens`	No	Max input tokens for this task (100-3000000). Defaults to the value the session was created with.
`maxOutputTokens`	No	Max output tokens for this task (100-1000000). Defaults to the value the session was created with.
`terminateOnCompletion`	No	Auto-terminate after task (default: false)

Output Schema

TableJSON Schema

Name	Required	Description
`data`	No	Task output payload (instance-authored shape)
`type`	No	Result type, e.g. 'task_completed', 'task_failed', 'guardrail_trigger'
`error`	No
`status`	No	Present on guardrail results: 'awaiting_input'
`taskId`	No
`message`	No
`pending`	No	True when the task is still running — poll get_task_status
`success`	No
`sessionId`	No
`environment`	No
`liveViewURL`	No	Page for watching the run live, present while it is still running or awaiting input. The only URL here that is safe to show a user or open in a browser.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 6, 2026

changedInput schema / properties / files / description

Previous value: -"Optional file IDs to attach (from /files/upload). Max 5 files."New value: +"Optional file IDs to attach: ids returned by POST /files/upload, or any file already in one of the user's environment catalogs (GET /environments/:id/files). Max 5 files."

Changed1 schema field changedAug 26, 2026

addedOutput schema / properties / liveViewURL

Added value: +{
+  "description": "Page for watching the run live, present while it is still running or awaiting input. The only URL here that is safe to show a user or open in a browser.",
+  "type": "string"
+}

Changed4 schema fields changedAug 23, 2026

addedInput schema / properties / maxDuration

Added value: +{
+  "description": "Max duration for this task in minutes (3-60). Defaults to the value the session was created with.",
+  "type": "number"
+}

addedInput schema / properties / maxInputTokens

Added value: +{
+  "description": "Max input tokens for this task (100-3000000). Defaults to the value the session was created with.",
+  "type": "number"
+}

addedInput schema / properties / maxOutputTokens

Added value: +{
+  "description": "Max output tokens for this task (100-1000000). Defaults to the value the session was created with.",
+  "type": "number"
+}

addedInput schema / properties / startingUrl

Added value: +{
+  "description": "URL to navigate to before starting this task (optional)",
+  "type": "string"
+}

Changed1 schema field changedAug 8, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "description": "Task outcome envelope: a completion (success/type/data), a pending marker (poll get_task_status), or an awaiting_input guardrail. `data` is the task output; its shape is task-defined (freeform text or the caller-supplied structured schema).",
+  "properties": {
+    "data": {
+      "additionalProperties": true,
+      "description": "Task output payload (instance-authored shape)",
+      "type": "object"
+    },
+    "environment": {
+      "properties": {
+        "environmentId": {
+          "type": "string"
+        },
+        "name": {
+          "type": [
+            "string",
+            "null"
+          ]
+        }
+      },
+      "type": "object"
+    },
+    "error": {
+      "type": "string"
+    },
+    "message": {
+      "type": "string"
+    },
+    "pending": {
+      "description": "True when the task is still running — poll get_task_status",
+      "type": "boolean"
+    },
+    "sessionId": {
+      "type": "string"
+    },
+    "status": {
+      "description": "Present on guardrail results: 'awaiting_input'",
+      "type": "string"
+    },
+    "success": {
+      "type": "boolean"
+    },
+    "taskId": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "type": {
+      "description": "Result type, e.g. 'task_completed', 'task_failed', 'guardrail_trigger'",
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

First observedAug 8, 2026

TDQS

A4/5.0

Behavior4/5

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

It adds concrete behavioral disclosure beyond the annotations: 'The real Chrome browser may navigate, fill forms, and submit data on third-party websites as the task requires.' This warns the agent about real-world side effects and aligns with openWorldHint and destructiveHint.

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?

Two purposeful sentences: the first states the operation and prerequisite, the second warns about real-world behavior. No redundant information.

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?

For a tool with 12 parameters, full schema coverage, an output schema, and safety annotations, the description provides enough context for selection and invocation. It could mention asynchronous behavior, but the sibling get_task_status and output schema reduce that gap.

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 the parameter descriptions already carry the meaning. The text adds no new parameter details beyond the session prerequisite, so the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a clear action ('send a new task') and target ('existing browser session'), and references create_session as the prerequisite. It does not explicitly differentiate from sibling tools like browser_task, but 'new task to an existing session' is reasonably specific.

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?

The description clearly implies when to use it: after create_session, to add a task to that session. It gives the prerequisite context but does not name alternatives or exclusions such as using browser_task for standalone tasks.

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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