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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so this is a lower bar, yet the description adds substantial behaviour beyond them: pagination loop semantics, the gross/net fee relationship, per-row fee attribution, page_totals being page-scoped, and PAPER-mode behaviour where fees are modelled and expected_pnl coincides with realized_pnl.

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?

Purpose and the pagination contract are front-loaded, and every sentence carries content. The back half is effectively a field glossary that partially duplicates the output schema, and the very long em-dash-chained sentences make it denser than it needs to be.

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?

For a paginated read tool with an output schema and full annotation coverage, the description is complete: an agent knows how to call it, how to exhaust the pages, and how to interpret realized_pnl, the fee fields, page_totals and the expected_pnl gap on SELLs.

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 runtime_id and cursor are already documented, and limit is left entirely to the schema. The description reinforces the cursor/has_more contract but adds no syntax, bounds or defaults beyond what the schema states, so the baseline 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?

Names a specific verb and resource ('Lists completed fills for one runtime') plus the ordering ('newest first') and the payload ('the profit realised on each'). An agent can tell this apart from spotgrid.list_orders (orders, not fills) without opening either schema.

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?

Gives strong operational guidance for pagination: pass next_cursor back and keep going until has_more is false, explicitly warning that 'one page is not the whole history'. It does not, however, say when to prefer this over spotgrid.list_orders or spotgrid.list_audit, so tool-selection guidance is only implicit.

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