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

Annotations already mark it read-only and idempotent; the description adds substantial behavioral context: plan-based silent filtering with `_warnings`, cache/refresh cadence, per-company `classification` only for Pro+, and the exact endpoint/credit cost. 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 long but front-loaded ('Discovery') and each sentence adds a distinct fact: return columns, caching, plan filtering, Pro+ differences, endpoint, and cost. Slightly dense, but no padding.

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?

With no output schema, the description names every major return column, jurisdiction-specific identifiers, filtering behavior, warnings, and plan-dependent fields. It is complete enough for an agent to invoke and interpret results confidently.

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 100% for the single optional `jurisdiction` parameter, and the description restates the same values and default behavior. It adds no new semantic information beyond the schema, so baseline 3 applies.

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?

Opens with 'Discovery: return every company covered', a specific verb and resource, then details optional jurisdiction filtering. This makes the tool's role as a comprehensive company-list endpoint unambiguous and distinct from the more targeted search/lookup siblings.

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 frames this as a discovery endpoint and gives operational guidance (omit jurisdiction for all plan-covered companies, cache and refresh at most once daily). However, it never explicitly names when to prefer list_companies over search_stocks or lookup_company, so the when-vs-alternatives guidance is implied rather than explicit.

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