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

Description adds key behavioral context beyond annotations: 'Lean mode — no bundle stored' indicates no persistence. The return object fields (summary, key_points, truncated, word_count) are listed. Annotations indicate read-only and open-world, which description does not contradict.

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?

Four concise sentences plus a return object and examples. Front-loaded with action and mode, followed by usage guidance and alternatives. No unnecessary text; 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 (fetch+summarize), annotations (readOnly, openWorld), and output schema, the description covers all needed context: it specifies public HTTPS only, provides usage guidelines, lists return fields, and shows example prompts.

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% (both url and max_tokens described). Description does not add new parameter detail but provides example prompts that implicitly show url usage. No additional semantics for max_tokens beyond 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?

The description clearly states the action ('Fetch a public HTTPS URL and return a prose summary with key points') and distinguishes itself from siblings (url.extract for raw text, url.qa for specific questions). The verb 'summarize' aligns with the resource 'URL' and title.

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 when to use ('Use when you need a condensed understanding of a web page') and provides specific alternative tools ('For raw text, use url.extract. For asking a specific question about a page, use url.qa'). Includes example prompts that guide correct invocation.

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