Loads a local development URL in a headless browser after validating it against the allowed localhost hosts. Use it to point the browser at a localhost page for automated testing.
Navigate the browser to a local dev URL (validated against the localhost allowlist).
| Name | Required | Description | Default |
|---|---|---|---|
| url | Yes | URL to load, e.g. http://localhost:8787 |
Changes observed during successful MCP inspections.
v0.4.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description must disclose behavior, and it does reveal the key constraint that URLs are validated against a localhost allowlist. However, it does not state what happens on validation failure, whether navigation waits for page load, or how it affects the current tab, leaving those behavioral traits undisclosed.
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?
The entire description is a single thirteen-word sentence with no filler. It front-loads the action and integrates the scoping constraint immediately, earning its place without redundancy.
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?
For a one-parameter navigation tool without an output schema or annotations, the description covers the essential purpose and the critical allowlist constraint. It omits failure-mode behavior but is otherwise sufficient for an agent to invoke the tool correctly.
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?
The schema covers the single `url` parameter with a description and example, satisfying the 100% coverage baseline. The description adds meaning by specifying that the URL is validated against the localhost allowlist, a constraint not present in the schema, so the agent understands the value must be a local dev URL.
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?
The description uses a specific verb ('Navigate') and resource ('the browser to a local dev URL'), clearly identifying the action and its target. The 'local dev URL' qualifier and allowlist mention differentiate it from navigation siblings like reload, back, forward, and new_tab, though it does not name them explicitly.
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?
The description implies the tool is for local dev URLs only, which tells the agent when this is appropriate, but it provides no explicit guidance on when to choose navigate over siblings such as new_tab, switch_tab, or reload. Sibling differentiation is left to inference from the 'local dev URL' phrase.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.