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

Annotations already mark it read-only, idempotent, and non-destructive; the description adds important runtime behavior: possible truncation with `_warnings`, 403 PLAN_TIER_INSUFFICIENT_COVERAGE for out-of-coverage companies, and equivalence to POST /api/v1/data/filings. 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 every sentence carries operational information: purpose, when-to-use, parameter semantics, truncation, errors, and API equivalence. It is front-loaded with purpose and usage before caveats.

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?

Even without an output schema, it tells the agent what to expect (rows, ids, fact counts, amendment note, `_warnings`) and where to find field details. It also covers error conditions and plan-scope behavior, so an agent has enough to call it 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 100% of parameters with descriptions, so baseline is 3. The description adds value by specifying accepted form_type values (10-K, 10-Q, 20-F, 40-F) and Korean DART mapping, which goes beyond the schema's generic examples.

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 ('List available SEC filings for one company and fiscal year') and enumerates returned fields (rows, ids, fact counts, amendment note). It also distinguishes itself from downstream siblings by naming them, so an agent can tell it apart from get_filing_facts and query_line_items.

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 says 'Use this first when you need filing_id or to see which quarters/forms exist before calling' a list of sibling tools, giving a clear when-to-use. It also documents form_type coverage and error behavior, making the selection context unambiguous.

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