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

With no annotations, the description carries full burden. It declares the tool follows the full redirect chain and returns final URL, hops, and metadata. This is appropriate for a read-only web intelligence tool. No contradictions.

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 effective sentences: one for purpose and output, one for cost context. No fluff, every word earns its place. Front-loaded with the core action.

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 tool with one parameter and no output schema, the description covers the purpose, return values (final URL, hops, metadata), and cost model. It lacks details like pagination or error behavior, but is sufficient for basic selection and invocation.

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 100% for the single parameter 'url.' The description adds context about the tool's operation (following redirects) but does not add new meaning beyond the schema's 'Target URL or hostname.' Baseline score of 3 is appropriate.

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 specific verbs and resources: 'Follow a URL's full redirect chain; return final URL, hops, and metadata.' It clearly distinguishes from siblings like unfurl_url (which may not follow full chain) or check_domain (which checks domain properties). The action and output are explicitly stated.

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 includes context about pricing and free tier ('web-intel; $0.003/call... 50 free/day'), which helps an agent assess cost. However, it does not specify when to use this tool versus alternatives like unfurl_url or check_domain, nor does it mention prerequisites or exclusions.

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