browser_openOpens a page in the session-owned browser and returns its indexed action space, reusing existing logins and closing the previous tab first.
Open a page in the browser this MCP session owns and return its indexed action space. The session reuses that browser and its logins across calls; the previous tab is closed first.
| Name | Required | Description | Default |
|---|---|---|---|
| url | Yes | Absolute page address (http(s); file:// works for local pages). |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare openWorldHint, idempotentHint=false and destructiveHint=false, but the description adds details absent from them: the browser and its logins persist across calls, and the prior tab is closed on each open. That tab-closing side effect is exactly the kind of state change an agent needs to know. It stops short of 5 by not covering navigation failures, popups, or auth prompts.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two tight sentences with zero filler. The key constraints (session ownership and tab replacement) are front-loaded, and the return value is stated in the same breath.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
With no output schema, the description usefully explains that the call returns an indexed action space, and it covers the session-persistence model. Remaining gaps (error behavior, how the indexed action space is consumed) are minor for a one-parameter tool.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
There is a single parameter with 100% schema coverage, and the schema already documents that it must be an absolute http(s) or file:// address. The description adds no syntax or format guidance beyond that, so the baseline of 3 applies.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb and resource (open a page) plus scope: the browser owned by this MCP session. It clarifies what is returned (an indexed action space) so the agent knows this is not a pure navigation call. It does not explicitly differentiate itself from siblings like browser_page or browser_act, keeping it just short of a 5.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Usage is implied by 'open a page' and 'the previous tab is closed first', which hints at a one-page-at-a-time workflow. However, it never says when to choose this over browser_page (inspect) or browser_act (interact), and gives no prerequisites or exclusions.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.