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

Annotations only declare the safety profile (readOnly, non-destructive, open world); the description adds substantial behavior beyond that: parallel fetching, per-page error isolation with partial success, billing semantics ('charged only if at least one page was read'), price, payment rail (x402 USDC on four chains), and a free sample invocation. That is exactly the extra context annotations cannot carry.

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?

Front-loaded with the core action and the sibling comparison, then cost, then params, then payment mechanics. Every sentence carries load, though the parameter line partially restates the schema and the 2-vs-1 URL count adds noise.

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 no output schema, the description must describe returns, and it does: Markdown with title and description, plus partial-failure behavior. Payment, cost, discovery alternatives, and a working example are all present, so nothing an agent needs to call it correctly is missing.

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 reinforces the ranges and default (max_chars 500–30000, default 6000) and supplies a concrete example payload. One minor wrinkle: the prose says '2 to 5 pages' while the schema (and the later param line) allow 1 to 5 URLs, a small internal inconsistency.

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 verb (read), resource (pages/URLs), cardinality (2 to 5), and output form (clean Markdown with title and description) in one call. It explicitly contrasts with the per-URL alternative web-scrape, so an agent can route between web_read_batch and web_scrape without opening either schema.

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?

Names the exact conditions that select it ('URLs you already know', 'cheaper and faster than calling web-scrape once per URL') and routes discovery to siblings: site-map for one site, search-read for a question. Both when-to-use and when-not-to-use are covered.

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