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

Annotations cover read-only and open-world safely. The description adds valuable behavioral context beyond annotations: paywall handling ('A Billboard Pro page returns its public full body when available; teaser-only pages are marked paywalled'). This is exactly the kind of non-obvious behavior an agent needs. Could add rate limits or auth requirements, but this is strong.

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 tightly packed sentences. Front-loaded with the core action, followed immediately by critical paywall behavior, then sibling routing. No wasted words.

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?

Complete for a single-URL article fetcher with an output schema. The description covers the main behavioral surprise (paywall marking) and routing. It could note whether the URL must be from a specific domain or include protocol details, but this is minor.

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 coverage is 100%, so baseline is 3. The description reinforces the url is canonical and specific to Billboard articles, but adds no syntax or format detail beyond the schema.

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?

Specific verb (Fetch) and resource (Billboard article metadata and body paragraphs) with the key input (canonical url) named. It distinguishes itself from billboard_headlines and billboard_sections by naming them as sibling navigation tools.

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: 'Use billboard_headlines to find stories or billboard_sections to select a section.' This tells the agent exactly when to use this tool vs alternatives.

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