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

The description adds substantial behavioral detail beyond the readOnly/idempotent annotations: events are grouped into display rows, ordered by significance tier, each row cites an evidencing record where one exists, and related events are folded into rollup rows with member_count and group_key. This gives the agent a strong mental model of the tool's behavior.

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 two dense sentences that front-load the core purpose and then provide the necessary input and rollup-expansion instructions. Every sentence contributes meaningful information with no filler or repetition.

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?

Given there is no output schema, the description does a good job explaining the expected return structure: display rows, significance tiers, evidence citations, and rollup expansion. It covers both parameters and gives enough context for an agent to call the tool correctly and interpret its results.

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?

The input schema already describes both parameters with 100% coverage. The description adds extra value by contextualizing node_id as coming from search_companies and by explaining that group is a group_key from a previous response used to expand a rollup. This goes slightly beyond the schema's field-level documentation.

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 clearly identifies the tool as a register event feed for one company, listing specific content types (filings, status changes, other register happenings). It also describes the output structure (display rows, significance ordering, evidencing record citations), which distinguishes it from sibling tools like company_financials or company_profile.

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 clear input guidance by stating that node_id must come from search_companies hits and explicitly warns against using the entity_id of company_profile. It also explains how to use the group parameter for expanding rollup rows. It does not explicitly name alternative tools or state when not to use it, but the usage context is clear enough.

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