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Read browser

browser_read
Read-onlyIdempotent

Open a page in a real browser and read it after its JavaScript has run. Use it when web_fetch comes back empty or with only a nav bar, which is what a page that builds itself in the browser looks like to a plain fetch. web_fetch is free and is the right first try; this costs, because it runs a browser

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "url": "<url>"
    },
    "name": "browser_read"
  }
}

Input Schema

NameRequiredDescriptionDefault
urlYesThe page to open
waitNoOptional CSS selector to wait for before reading, for content that arrives late

Schema Changelog

Changes observed during successful MCP inspections.

  1. Added
  2. Removed
  3. Added

TDQS

A4.4/5.0
Behavior4/5

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

Annotations already declare readOnlyHint and idempotentHint, and the description adds meaningful context: it runs a real browser, executes JavaScript, and incurs cost. It does not describe the return format, but for a read tool with safety hints that is a minor omission.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences with no fluff: the core action comes first, the deciding condition is second, and the cost trade-off is third. Every sentence contributes useful guidance.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-parameter read tool with coverage annotations, the description covers purpose, usage policy, and key behavior. The only notable gap is the absence of any description of what the returned content looks like, since there is no output schema, but this is not severe.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so parameters are already fully documented. The description adds the contextual meaning of JS execution but does not add detail beyond what the schema provides, matching the baseline for fully covered schemas.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description begins with a specific verb and resource: 'Open a page in a real browser and read it after its JavaScript has run.' It clearly distinguishes browser_read from sibling web_fetch by highlighting JS rendering, and the name/title gap is resolved by the description.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly tells the agent when to use this tool: when web_fetch returns empty or nav-bar-only content. It also gives the decision rule 'web_fetch is free and is the right first try; this costs,' which directly chooses between siblings.

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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