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

Annotations already cover readOnlyHint/openWorldHint, and the description adds real behavioral value: subscriber-only stories without a free preview return 403 rather than an empty body, and only public articles are returned. This preempts a common failure mode, though pagination/truncation behavior for long bodies is unstated.

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 tight sentences: purpose first, then the 403 caveat, then the sibling routing. No filler, and the most decision-relevant information is front-loaded.

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 an output schema present, return values need not be described, and the description covers input, error behavior, and alternatives. It is complete enough to call correctly, with only minor gaps around body-length limits or caching.

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 fully documented as a canonical www.axios.com URL. The description's 'canonical `url`' phrasing reinforces but does not extend the schema, so the baseline of 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 verb (Fetch) and resource (Axios article metadata and full body paragraphs) scoped to a canonical url. It explicitly names sibling tools axios_headlines and axios_categories, so the agent can distinguish it from discovery/browsing tools without inspecting 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?

Routes the agent to axios_headlines for discovery and axios_categories for topic browsing, implying this tool is for when you already hold an article URL. It stops short of an explicit 'use when you have a URL and need the full body' statement, but the alternative routing is clear.

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