Browser Session MCP

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Loads an absolute URL in the active session tab and returns after the load event, enabling agents to fetch pages and continue after redirects.

Instructions

Load a URL in the session's active tab and return once the page's load event fires. Use new_page instead to keep the current page and load the URL in a new tab, and wait_for after this when content arrives after the load event. If every tab was closed, a new one is opened. url must be absolute (https://, http://, data:, about:); timeout bounds only the wait for the load event. The returned url is the final one after any redirects. Fails with Chrome's net error (e.g. net::ERR_NAME_NOT_RESOLVED) if the page can't load, or if timeout passes first, in which case the page may still be loading.

Input Schema

Name	Required	Description
`url`	Yes	Absolute URL to load, including the scheme.
`timeout`	No	Milliseconds to wait for the load event before failing. Default: no limit.
`sessionId`	Yes	The id returned by open_browser_session. Errors if no open session has it.

Output Schema

Name	Required	Description	Default
`url`	Yes	The page's URL after any redirects.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv0.1.5Oct 24, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "properties": {
+    "url": {
+      "description": "The page's URL after any redirects.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "url"
+  ],
+  "type": "object"
+}

Changed3 schema fields changedOct 23, 2026

addedInput schema / properties / sessionId / description

Added value: +"The id returned by open_browser_session. Errors if no open session has it."

addedInput schema / properties / timeout / description

Added value: +"Milliseconds to wait for the load event before failing. Default: no limit."

addedInput schema / properties / url / description

Added value: +"Absolute URL to load, including the scheme."

First observedv0.1.2Oct 23, 2026

TDQS

A4.6/5.0

Behavior4/5

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

With annotations covering read/write and open-world traits, the description adds real behavioral context: auto-opening a tab when none exist, the fact that timeout bounds only the load-event wait (page may still be loading on failure), post-redirect returned url, and net-error failure modes like net::ERR_NAME_NOT_RESOLVED. It does not discuss session-state persistence or auth, but those don't apply here.

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 core action and completion semantics; every sentence carries distinct information (routing, schemas, timeout scope, redirect behavior, failure modes). It is dense prose without visual structure, which is slightly harder to scan, but nothing is wasted.

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 3-parameter navigation tool with an output schema, the description covers the operation, alternatives, parameter constraints, edge cases, and failure modes. Nothing an agent needs to invoke it correctly is missing, and return-shape explanation is a bonus rather than a gap-filler.

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 100%, so the baseline is 3, but the description goes beyond it by enumerating allowed schemes (https, http, data, about) and clarifying that timeout scopes only the load-event wait rather than the whole navigation. sessionId semantics are left to the schema, which handles them adequately.

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 ('Load a URL in the session's active tab') plus the completion condition ('return once the page's load event fires'). Immediately contrasts with new_page, so an agent can distinguish it from the sibling that loads a URL in a new tab without opening a 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?

Explicitly names two alternatives and the condition selecting each: use new_page to preserve the current page, and wait_for afterward when content arrives after the load event. It also covers the edge case where all tabs are closed, leaving no routing ambiguity.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.