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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description usefully notes the content is public and that body paragraphs (not just metadata) are returned, but says nothing about failure modes for malformed URLs, paywalled/premium content, or rate limits.

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?

A single dense sentence with zero filler that front-loads the resource and enumerates the returned content. Nothing could be removed without losing information.

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 one-parameter read-only fetch with 100% schema coverage, full annotations, and an output schema that documents the return shape, the definition is nearly complete. Only the absence of any guidance on what a valid/canonical URL looks like or when to prefer sibling endpoints keeps it from being fully self-sufficient.

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 single "url" parameter is documented as the canonical Polygon article URL in the schema itself. The description adds no format, slug, or validation detail beyond what the schema already provides, so 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?

States a specific resource (a single public Polygon article) plus the payload (metadata and body paragraphs), which distinguishes it from polygon_headlines, polygon_news, and polygon_sections as a detail fetch. It stops short of naming or explicitly contrasting with those siblings.

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?

Usage is only implied: the word "One" and the required canonical URL signal this is the by-URL retrieval tool, whereas the sibling list tools are for discovery. There is no explicit when-to-use or when-not-to-use statement.

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