cotlet_browser_navigateOpens a public http or https address in the user's Substack Cloud Browser and returns the URL and title it ended on. Only Substack pages open. Every started minute of the session costs credits; it ends when closed or 3 minutes after the last call in the browser.
| Name | Required | Description | Default |
|---|---|---|---|
| url | Yes | A public http or https address, e.g. https://example.com. In an app's browser, a page of that app. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover read-only, open-world, non-idempotent and non-destructive traits, and the description adds genuinely non-structured behaviour: a per-started-minute credit cost and an idle termination after 3 minutes or on close. It stops short of saying how failures, redirects, or non-Substack URLs are handled ('Only Substack pages open' is stated but not what happens if you pass something else).
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?
Three tight sentences: what it does and returns first, then the domain restriction, then the cost and lifetime caveats. Nothing is redundant and the routing-relevant information is front-loaded.
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?
No output schema exists, and the description compensates by naming the return values (final URL and title). For a one-parameter browser navigation tool with rich annotations, that is nearly complete; only error/non-Substack behaviour and the relationship to cotlet_browser_open are unaddressed.
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?
Schema coverage is 100% and the single 'url' parameter is already documented with a format and example, so the schema does the heavy lifting. The description's 'Only Substack pages open' arguably narrows the schema's broader 'public http or https address, e.g. https://example.com', which adds a note of ambiguity rather than clarifying meaning.
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?
It states a concrete verb ('Opens') and resource ('a public http or https address in the user's Substack Cloud Browser'), and even names what is returned. It does not, however, distinguish itself from the sibling cotlet_browser_open, leaving the agent to guess which of the two starts a browsing session.
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 gives an implied usage context ('Only Substack pages open') but never says when to pick this over cotlet_browser_open or when to precede it with cotlet_browser_open. The credit/expiry note hints at cost-awareness but does not route the agent to alternatives.
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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