intercept_start

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

With no annotations present, the description carries the full burden and does so well. It discloses that rules are routed on the context, apply to later-opened tabs, that re-calling replaces prior rules, that intercept_stop removes them, and that blocking 'document' would abort navigation.

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 description is compact and front-loaded with the core behavior. Every sentence adds distinct information: action, performance rationale, scope, replacement semantics, and a critical limitation. There is no filler or repetition of schema details.

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 tool with three optional parameters, no annotations, and no output schema, the description is unusually complete. It covers lifecycle, scope, limitations, and practical use, giving an agent everything needed to invoke it 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?

Schema coverage is 100%, so the baseline is 3, but the description adds practical meaning beyond the schema: it explains why block_types like image/media/font/stylesheet matter for scraping performance and why block_urls is useful for trackers and ad frames. log_limit is also tied to intercept_log, adding useful context.

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 opens with a specific verb and resource: 'Block requests before they leave the browser.' It clearly distinguishes this from siblings like intercept_stop by stating that intercept_stop removes the rules, and from network monitoring tools by focusing on active blocking.

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?

It explicitly says when to use this tool: when scraping to remove most page bytes and to kill trackers/ad frames. It also explains the replacement behavior and routes users to intercept_stop for removal, and warns that 'document' cannot be blocked. This gives clear selection guidance.

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