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

Annotations already declare the safety profile (readOnly, idempotent, non-destructive, open-world), so the bar is lower. The description adds genuine behavioral value by disclosing the aggregation scope ('across all years', pre-aggregated) and the returned measures ('total dollars and payment count per manufacturer/GPO'), which the annotations do not convey.

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, front-loaded with the aggregation semantics and granularity before the use case. Every sentence carries information; no filler or restatement of the tool name.

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?

No output schema exists, so the description carries the burden of describing returns, and it does so ('total dollars and payment count per manufacturer/GPO'). Combined with the annotation coverage and the documented limit parameter, the definition is nearly complete, with only the absence of sibling routing as a minor gap.

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?

With 100% schema description coverage, the single 'limit' parameter is fully documented in the schema (default 20, max 50). The description adds no parameter-level detail beyond what the schema provides, 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?

The description names a specific resource (payment summary grouped by reporting company) with a clear scope ('across all years'). The grouping dimension ('grouped by reporting company', 'per manufacturer/GPO') implicitly distinguishes it from siblings like open_payments_by_specialty and open_payments_state_totals, though those alternatives are never named.

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 final sentence gives a use case ('rank companies by their pharma-influence spend'), which is a clear context hint. However, it offers no exclusions or routing guidance against the many near-identical siblings (open_payments_top, open_payments_national_summary, open_payments_by_specialty), leaving the agent to infer when this tool is preferred.

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