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

Annotations already declare readOnly/idempotent/non-destructive, and the description goes well beyond: request metrics with no value are never silently dropped but returned under `unavailable` with reason, alternatives, and docs_url, including the bank/broker/insurer revenue-family example. That is exactly the kind of non-obvious behavior an agent needs to interpret results correctly.

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 the core scope, then the failure-mode behavior. The parenthetical enumeration of revenue-family members is long but earns its place by making the `unavailable` semantics concrete; overall it is dense but not padded.

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 and the description still usefully frames the return structure (metrics vs unavailable, with source/knowledge time/lineage). The only shortfall is the unexplained fiscal_year/fiscal_period parameters, which leaves a small hole for a point-in-time tool where period selection matters.

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 carry the load: it does clarify the YYYY-MM-DD format for `as_of_date` and the role of `metrics` as a requested-metric list. However, `fiscal_year` and `fiscal_period` (with its 'FY' default) are never explained, leaving meaningful gaps.

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 pair ('point-in-time fundamentals') plus the exact scoping axes (ticker, as_of_date). This is plainly distinct from the siblings (earnings events, filing metadata, index constituents), so an agent can select it without ambiguity.

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 description gives a strong operational rule — inspect `unavailable` before concluding a figure does not exist — which is a real usage directive. It does not explicitly compare itself to the sibling tools or state exclusions, but the scope is narrow enough that the context is clear.

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