get_fact

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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the bar is lower, but the description adds real behavior: non-FY periods are refused with an error, and missing combinations return an error result rather than null. It stops short of noting pagination/units or the exact error shape.

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 purpose followed by parameter notes and an error caveat; every sentence carries information. Slightly paragraph-heavy for what could be tighter bullets, but no filler.

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?

An output schema exists, so return-format detail is unnecessary, and annotations cover the safety profile. Combined with the error/refusal guidance, the agent has enough to invoke it correctly; only entity_id/fiscal_year semantics and value units are unaddressed.

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 0%, so the description must compensate and largely does: hub_concept_code is explained as a standardized code with concrete examples, and fiscal_period_type carries default and constraint ('defaults to FY; annual only, others refused'). entity_id and fiscal_year are left implicit, but their meaning is self-evident.

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+scope: 'Get a normalized financial value for an entity at a given period.' The concept-code dimension and period semantics make it identifiable apart from siblings like get_metric_history or get_fact_decomposition 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?

Explicitly routes the agent: 'Use search_concept first if you don't know the code.' It also encodes a when-not rule for the period parameter (non-annual types are refused) and an anti-pattern ('never fill the gap with an estimate').

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