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

Annotations only provide readOnlyHint, so the description carries the rest and does so richly: parallel-array alignment, null-vs-0 convention, WITHHELD pre-split per-share cells with a pointer to `basis`, the {error,...} return for IFRS/no-fact filers, source, ~45-day lag, and 24h cache. This is well beyond what the annotation declares.

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?

Front-loaded with purpose then return shape, and nearly every clause carries distinct semantic value (array alignment, units, null handling, withheld cells, error shape, alternatives, source). The density is justified for a rich return payload, though it reads as a dense block rather than cleanly segmented lines.

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 must (and does) fully specify the return contract including the field list, index alignment, units, null semantics, and the error variant. Nothing an agent needs to interpret or trust the response is missing.

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?

Only one parameter (ticker) with 100% schema description coverage, so the schema fully documents it. The description adds no syntax, format, or edge-case meaning for the ticker argument itself; baseline 3 applies when the schema does the heavy lifting.

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+resource ('Full XBRL financial history for one ticker') and immediately scopes what it returns. It explicitly routes to siblings ('For cash deployment use get_capital_allocation; for per-share fair value ol_intrinsic_value; for industry operating metrics ol_operating_kpis'), so an agent can distinguish it from get_capital_allocation and ol_operating_kpis 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 specific alternatives with the condition that selects each, which effectively tells the agent when to choose something other than this tool. The scope statement (full XBRL history for one ticker) plus the alternative routing leaves no ambiguity about task fit.

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