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

Annotations only declare readOnly and openWorld. The description adds real operational context beyond that: metered stories return in full, while subscriber-only stories return a permission error, plus a note that both metadata and body paragraphs are returned. This access-tier nuance is exactly the useful context annotations cannot carry; only the output shape detail is left to the schema.

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?

Two sentences, front-loaded with the fetch purpose and then the 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?

With an output schema present, return values needn't be explained. Purpose, sibling routing, and the access-tier behavior are all covered, so an agent has everything needed to call it correctly.

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% and the description merely restates 'canonical url' with no added syntax or format guidance. Baseline 3 applies since the schema does all the parameter documentation.

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 and resource: fetching Irish Times article metadata and body paragraphs from a canonical URL. It explicitly differentiates from siblings (headlines for story lists, sections for topics, author for profiles), so an agent can route 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?

Names three sibling tools and the distinct purpose of each, effectively telling the agent when to use this one (a specific article URL) versus the list/topic/profile tools. The alternative routing is explicit rather than inferred.

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