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

Annotations already provide readOnlyHint=true and idempotentHint=true; the description adds substantial context beyond that: 10 credits per page, empty pages and 404 EVENTS_COMPANY_NOT_FOUND still being charged, the plan's history-window limit, and the need to read _warnings for history notices and differing Item lists.

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 front-loaded with purpose and usage guidance, and nearly every sentence carries useful information. However, the middle section is semicolon-heavy and mixes cost, warnings, plan limits, and error behavior into a run-on structure, and the trailing API path/doc reference adds minor clutter.

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, the description names the returned fields, ordering, warning field, cost, error-charging behavior, and plan requirement. The parameter selection rule and sibling routing complete the picture, making this fully actionable for an agent.

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?

All four parameters have full schema descriptions, including the ticker/cik mutual exclusivity noted in both properties. The tool description restates 'Requires exactly one of ticker / cik' but does not add meaningful detail about page, page_size, or formatting beyond what the schema already provides.

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 a specific action and scope: 'List one company's corporate event filings, newest first, with filing IDs, dates, Item lists and amendment status.' It clearly distinguishes itself from siblings by naming get_event_filing and search_events as the alternatives for nearby use cases.

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 explicitly states the selection constraint 'Requires exactly one of ticker / cik' and tells the agent when to use siblings instead: get_event_filing for reading sections and search_events for Item/date filters or cross-company searches. It also surfaces the plan requirement and charged-error behavior, so the agent can decide whether the call is appropriate.

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