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

Annotations cover read-only/open-world/non-idempotent, but the description adds the crucial behavioral facts an agent must know before calling: the $0.15 USDC cost via x402 or prepaid credits and that it is excluded from the free trial. This pricing/eligibility context goes beyond structured fields, though rate limits and latency are not mentioned.

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 dense sentences, action and workflow front-loaded, with differentiation and pricing appended. Every sentence carries information (capability, comparison, cost), though the parenthetical output list makes it borderline long.

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, the description needn't explain return values, and annotations plus full schema coverage handle parameters. The added differentiation and pricing notes make it complete for an agent to decide and call, leaving only minor gaps like pagination or latency.

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 goes slightly further by framing 'last N days of coverage' and 'reads the top articles in full', giving the days and articles parameters semantic grounding in terms of what they control.

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+resource ('brief me on a topic') plus an explicit rundown of inputs (HN, Reddit, world news), processing (reads top articles in full), and output shape (summary, key developments, viewpoints, open questions, citations). It also names the sibling it differs from ('Deeper than /news/brief'), so an agent can separate it from news-brief 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?

The 'Deeper than /news/brief' clause routes the agent toward this tool when depth is required, and the paid-only note ('not in the free trial') is an important selection constraint. It stops short of stating explicit when-not conditions or listing other alternatives like report-area or search-answer.

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