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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety and open-web profile are covered. The description adds useful behavioral context by disclosing that the response bundles profile fields plus recent articles, which is beyond the structured data. It does not mention rate limits or auth, so it is strong but not exhaustive.

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 short sentences, front-loaded with the primary purpose, followed by sibling disambiguation. No filler or redundancy.

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?

With one required parameter, an output schema to carry return structure, and annotations covering the safety profile, the description supplies everything an agent needs: what it returns and when to prefer siblings.

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?

There is a single parameter with 100% schema description coverage ('Canonical Polygon author URL'), so the schema already documents it fully. The description adds no format or syntax detail for the url beyond what the schema states; 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?

States a specific verb (Fetch) and resource (one Polygon author's public profile), then enumerates the returned fields (name, job title, headshot, biography, social links, recent articles). It also names three sibling tools it is not, so an agent can distinguish it from polygon_article, polygon_headlines, and polygon_news without opening schemas.

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 routes the agent: polygon_article for a single story's content, polygon_headlines and polygon_news for current outlet feeds. Each alternative is paired with the condition that selects it, leaving nothing to inference.

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