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

Annotations already cover the read-only/idempotent profile, and the description goes well beyond them: ordered significance tiers, folded rollup rows with member_count/group_key, citation notice carry-along rules, and a full insolvency_lookup state machine (pending/current/not_requested/not_looked_up) with its completion caveat.

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 feed/rollup behavior is front-loaded and useful, but the description runs long for a two-parameter read tool, with a dense multi-clause run-on describing insolvency_lookup states that could be tightened. Every sentence carries information, but parsing cost is high.

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 carries the return-shape burden and does so reasonably well: rows, citations, rollups, and the insolvency_lookup field with its note. A little more on ordering/pagination or row fields would make it fully self-sufficient.

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% and both param descriptions are already present in the schema, including the node_id vs entity_id disambiguation. The description adds little on group beyond reiterating the expansion behavior, so the baseline 3 is appropriate.

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?

Names a specific resource (the register event feed of one company) and enumerates its content: filings, status changes, other register happenings. The row grouping, significance ordering, and citation behavior distinguish it clearly from siblings like company_news or company_records.

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 routes the agent to search_companies hits for node_id and warns against company_profile's entity_id, and explains when to pass group_key to expand a rollup. It does not, however, state when another sibling tool would be the better choice for adjacent needs.

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