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

Annotations provide readOnlyHint and openWorldHint, but the description adds critical behavioral context beyond them: it is a paid tool costing $0.01 USDC exact on Base with a payTo address, it follows redirects up to 8 hops, is SSRF-safe, does not handle meta-refresh, and sends no payment headers. This fully discloses side effects and limitations.

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?

The description is dense and front-loaded with the most important operational fact (cost), followed by what it does, constraints, return values, and exclusions. Every sentence conveys necessary information, though the telegraphic style and payment address make it slightly less polished.

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 single-parameter, read-only tool with no output schema, the description is complete: it explains what is returned (chain, finalUrl, hopCount), the cost, the safety properties, and the exclusions. An agent has enough information to call it correctly and interpret the result.

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%, and the description repeats the schema's 'Public http(s) URL' wording without adding new parameter-level detail. It adds tool-level constraints like SSRF-safe and max hops, but not more about the url parameter itself, so baseline 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 states a specific verb ('follow Location redirects') and resource ('a public http(s) URL'), and it clearly distinguishes itself from siblings by noting 'Not /headers' and 'No meta-refresh'. An agent can understand exactly what the tool does and that it is not the headers tool.

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 clear usage constraints: manual, max 8 hops, SSRF-safe, public URL, and payment required. It explicitly disambiguates from the headers sibling with 'Not /headers', but it does not proactively say 'use headers tool if you need headers' or list other exclusion conditions. Most needed context is present.

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