browser_fetch

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

With no annotations, the description carries the full burden and does so well: it discloses CORS/CSP immunity, that browser cookies are neither sent nor stored, that a token must be passed via headers, and that plain http only reaches 127.0.0.1. It omits error/timeout behavior and the response shape, keeping it just below a 5.

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 tightly packed sentences with zero filler; the core capability is front-loaded and each clause adds a distinct constraint (scope, cookie policy, protocol limit).

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 fetch tool with no annotations and no output schema, the description covers the critical behavioral traits an agent needs to call it safely. The one gap is the return value/response format, which nothing else in the structured data supplies.

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 description coverage is 100%, so the schema already documents url, body, method, and headers; baseline is 3. The description adds the useful auth hint ('pass a token in headers') tied to the cookie policy, but gives no additional syntax for body/method beyond the schema.

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 action (make an HTTPS request from the extension background) and immediately distinguishes it from an in-page fetch by noting CORS/CSP bypass. It does not name sibling tools like browser_navigate or browser_execute_script, but the resource and scope are unambiguous.

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?

Gives a concrete when-to-use context ('API calls (Google, Stripe, Slack) where a fetch from the page would be blocked'), which tells the agent the exact scenario this tool exists for. It stops short of naming alternatives or stating exclusions, so it's clear but not fully routing-aware.

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