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

Annotations already declare readOnly/openWorld/idempotent/non-destructive, yet the description adds materially more: redirects are followed, public internet only, JS-only pages fall back to server HTML (no headless browser), PDFs are text-converted, cost is $0.002/call with 10 free/day and x402 payment on exhaustion, and errors return isError without charging. These are behaviors the annotations cannot express.

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 input→output contract, then capabilities, then limitations, then routing, then cost and error semantics. Every sentence carries a distinct fact (extraction engine, JS limitation, price, refund-on-error); none are filler.

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?

An output schema exists so return values needn't be explained, yet the description still summarizes what comes back. For a 3-param read tool with rich annotations, the description covers scope, limits, failure modes, and pricing with nothing an agent needs left out.

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 min/max/default for max_chars and the link-list behavior of include_links are already documented. The description's only added semantic is the usage hint 'Use max_chars to bound the output,' which is directionally useful but not deep enough to exceed the baseline for a fully documented 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 precise transformation ('Any public URL → clean readable markdown') plus the exact output bundle (title, author, date, word count, links), and names the extraction mechanism (Mozilla Readability). It is immediately distinguishable from web_meta and http_probe, which are named in the same description.

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?

Contains an explicit 'When to use' clause and routes to alternatives by condition: 'for its metadata only use web_meta; for uptime/redirects use http_probe.' No inference required from the agent.

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