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

Annotations declare readOnlyHint, openWorldHint, idempotentHint, destructiveHint. The description adds critical behavioral context: 'it does not execute JavaScript or bypass access controls' and explains caching behavior with 'bounded cached result' and 'cheaper for the origin.' No contradiction.

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: first states primary function, second covers usage constraints and parameter guidance. No wasted words; every sentence 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?

Given the tool's simplicity (2 params, output schema present), the description covers purpose, usage constraints, parameter semantics, and behavioral notes. There is no gap; it is sufficient for an agent to select and invoke the tool correctly.

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% with descriptions. The tool description adds further value: for url, it clarifies restrictions on private/SSRF-sensitive destinations; for fresh, it explains caching trade-offs. This goes beyond the schema descriptions.

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 clearly states 'Return the bounded heading hierarchy from h1 through h6' which is a specific verb+resource. It distinguishes from sibling tools like web.url.text or web.url.links by focusing solely on headings.

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 gives explicit usage constraints: 'Use only for public HTTP(S) resources; it does not execute JavaScript or bypass access controls.' It also guides parameter usage with 'Keep fresh=false to allow cache reuse; set fresh=true only when a new upstream fetch is required.' It does not list alternatives but the purpose is clear enough.

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