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

Annotations already declare readOnlyHint=true and openWorldHint=true, covering the safety profile. The description adds the specific metadata fields extracted but does not disclose network fetch behavior, error handling, or response format, which are relevant for an open-world tool.

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 concise sentences, front-loaded with the action and a clear usage cue. Every word earns its place; there is no unnecessary detail or repetition.

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?

For a simple single-parameter tool with annotations covering safety, the description provides purpose and usage context sufficiently. It lacks details about network behavior and potential failures, but these are not critical for a basic metadata extraction tool with no output schema.

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?

The schema covers the single 'url' parameter fully (100% coverage) with description 'URL to fetch and extract metadata from'. The tool description does not add additional parameter semantics beyond the schema's existing description, so the baseline 3 applies.

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 uses the specific verb 'extract' with the resource 'URL metadata' and lists concrete items (title, description, OG tags, favicon), making the tool's purpose unmistakable. It clearly distinguishes itself from sibling lookup tools like lookup_headers or lookup_tech_detect.

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?

Provides explicit usage context: 'Use when you need to preview or summarize a webpage.' This clearly signals the intended scenario but does not mention when not to use it or alternatives, so it stops short of a 5.

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