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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuinely useful context beyond that: the 2 MB input ceiling, the optional base URL for link resolution, the returned field set, and the x402 pricing requirement ($0.005 USDC per call on eip155:8453), which an agent needs before invoking.

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?

Two sentences, front-loaded with the core action, followed by the constraint and the cost. The output-field enumeration is a bit of a list but each item tells the agent what it gets, so it earns its place.

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 helpfully names the return fields, and it covers pricing and size limits. However, for a 5-parameter tool with 0% schema coverage and no output schema, the undefined 'mode' enum and 'maxChars' truncation knob are meaningful gaps an agent would need to guess at.

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 0%, so the description has to carry parameter meaning. It explains html (size limit) and baseUrl (resolves relative links) and implies format, but leaves 'mode' (main vs all) and 'maxChars' entirely unexplained, which is a real ambiguity given 'mode' is an opaque enum.

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 (convert/extract) and resource (HTML input), and explicitly distinguishes itself from its closest sibling: 'Same engine as web-extract, without fetching'. An agent can immediately tell this is the offline counterpart to web_extract.

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?

'Convert HTML you already have' and 'without fetching' clearly signal when this tool applies versus web_extract, and the 2 MB cap sets a boundary. It stops short of an explicit 'if you have a URL instead, use web_extract', but the contrast is strong enough to route correctly.

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