Read a URL

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds meaningful behavioral context beyond annotations: hidden-text stripping with threat reporting, stealth-browser fetching for blocked sites, and per-domain rate limiting. It does not contradict annotations. The only minor gap is no mention of failure modes or what 'grounded content with provenance' structurally looks like, though the output schema likely covers return shape.

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 paragraphs, each earning its place: first defines the action and output, second explains the hidden-text safety behavior and value proposition, third gives usage guidance, alternatives, and rate-limit caveat. It's appropriately sized for a tool with 5 parameters and meaningful behavioral nuance, though it leans slightly long relative to its sibling-differentiation needs.

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?

With an output schema present, return-value details are handled structurally. The description covers the tool's distinctive behaviors (stealth fetching, hidden-text stripping, provenance), usage guidance, rate limits, and alternatives. For a tool of moderate complexity with rich schema and annotations, the description is complete enough. It could add slightly more on error/failure behavior, but it is not a material gap.

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 all five parameters are documented in the schema. The description resists repeating schema detail and instead adds cross-parameter context (e.g., 'reported in `threats`' ties include_hidden and hidden-text stripping together). The `query` and `format` behaviors become clearer through the description's grounding framing, but the schema already does the heavy lifting. Baseline 3 is appropriate.

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+resource ('Fetch one web page through the stealth browser') and clearly states what it returns ('clean, grounded content with provenance'). It explicitly differentiates from siblings: 'use `search` to find URLs, or `research` to search and read in one call', naming the alternatives directly. The reference to 'sites that block plain fetchers' adds a clear use-case distinction.

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 explicitly states when to use this tool vs alternatives: 'Reads a URL you already have: use search to find URLs, or research to search and read in one call.' It also discloses the rate-limiting behavior ('5s apart by default'), setting expectations about latency. This is explicit when/alternative guidance with concrete operational context.

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