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

Description adds context beyond annotations: it does not execute JavaScript or bypass access controls, and clarifies cache behavior. Annotations (readOnlyHint, idempotentHint, etc.) already indicate safety, but the description elaborates on specific behaviors that matter for selection.

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 sentences, each serving a distinct purpose: purpose/scope, constraints, parameter guidance. No fluff. Front-loaded with the main function.

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 complexity (simple extraction with two parameters) and presence of output schema, the description sufficiently covers purpose, constraints, and usage. No need to describe return values since output schema exists.

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 for both parameters. Description adds extra context: url must be absolute public HTTP(S) and rejects private destinations; fresh=false allows cache reuse while fresh=true forces new fetch. This adds meaning 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?

Description clearly states it extracts bounded Open Graph and Twitter Card fields. The verb 'Extract bounded' and specific resource 'Open Graph and Twitter Card fields' distinguishes it from sibling tools like web.url.metadata which may extract all metadata. No ambiguity.

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?

Explicitly states to use only for public HTTP(S) resources and provides conditions for the 'fresh' parameter. Implicitly advises against using for internal resources. No explicit sibling alternatives but given the context of many sibling tools, the bounded nature makes usage clear.

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