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

Annotations already mark this read-only/idempotent; the description adds substantial non-obvious behavior: plan-tier truncation with `_warnings`, 403 PLAN_TIER_INSUFFICIENT_COVERAGE, 400 METRICS_UNSUPPORTED_FOR_<jurisdiction> with no credits charged, and plan requirements for formula_override. It also clarifies jurisdiction-specific form-type coverage. No contradiction with 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 description is dense but front-loaded: purpose and use case appear in the first two sentences before optional parameters and error handling. It is long because the tool is complex, and nearly every sentence carries operational information; minor redundancy with schema parameter descriptions keeps it from a 5.

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 12-parameter tool with no output schema, it covers required input, defaults, paging, date filters, plan limits, error codes, and jurisdiction caveats. It does not detail the response shape beyond paging and `_warnings`, but the operational guidance is sufficient to invoke correctly.

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 covers all 12 parameters, so baseline is 3; the description adds value by explaining period_type's form-type implications (10-K/20-F/40-F vs 10-Q, Korean DART equivalence), light_weight_mode's effect on audit fields, and plan gating for formula_override. This goes beyond the schema's own descriptions.

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?

The description opens with 'Time series of metrics for a ticker across many periods' — a specific verb, resource, and scope — and immediately frames the use case ('trends like gross margin or revenue over time'). It clearly distinguishes itself from sibling metrics tools by emphasizing multi-period time series and paging.

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?

It states 'Use for trends like gross margin or revenue over time, with paging,' giving clear context for when to call it. It does not explicitly name sibling alternatives or state when not to use it, so it stops short of full exclusion guidance.

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