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

Goes well beyond the readOnly/openWorld annotations by disclosing a data-quality trait (cancelled prints remain in the tape, marked), the entitlement model (Plus delayed 15 minutes, Pro real-time, Free rejected with an upgrade note), the history floor, and the truncation/continuation contract. These are exactly the behaviors an agent cannot infer from the schema or annotations.

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?

The purpose and the single-contract constraint are front-loaded in the first clause, and the following sentences each carry distinct operational facts with no filler. The paragraph is dense and packs entitlement, paging and data-quality notes into one block, which would read better as short separated sentences, but nothing is redundant.

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 six parameters, no output schema and full schema coverage, the description still fills the gaps that matter: what the rows contain, ordering, default and historical time bounds, paging, entitlement delay, and the cancelled-print caveat. An agent can call this correctly and interpret the result without further documentation.

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 the baseline is 3, but the description still adds meaning: the 4-day default window and the 2024 history floor bound startDate/endDate, and 'a cut answer names the endTime that continues it' explains the interaction between maxResults truncation and endTime paging rather than just restating the field format. The plan-based behavior additionally explains why a call may succeed without data.

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 ('Get the trade tape for ONE option contract by its OCC symbol') and adds discriminating scope: single contract rather than a chain, active or expired contracts, and newest-first ordering. The return fields (time, price, size, exchange, condition) are enumerated, so an agent can tell this apart from GetOptionChain, GetOptionChainSummary and GetOptionContractHistory without opening a 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 concrete operating context: default window is the last 4 days, history begins in early 2024, and US tickers only. It also warns how to interpret the data ('read volume from the bars, not a sum of prints') and how to page with endTime. It stops short of naming sibling alternatives such as GetOptionChain for multi-contract needs, so the routing is implied rather than explicit.

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