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

With no annotations, the description carries the full burden and does so well: it discloses the paid model ($0.01 via x402), that cursors are stable across restarts, that the response carries changed_count plus a new next_cursor, and a cost-avoidance polling strategy. It does not cover failure modes (stale/invalid cursor) or rate limits, so not quite maximal.

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?

Front-loaded with the core purpose, then bootstrap/cursor mechanics, then the HTTP/pricing trailer. Slightly redundant in restating the endpoint twice ('delta of /v1/edgar/events' then 'Keyset delta of /v1/edgar/events'), but every remaining sentence earns its place.

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?

For a one-param tool with no annotations and no output schema, the description covers bootstrap behavior, delta semantics, cursor persistence, and names the returned fields (changed_count, next_cursor), which substitutes adequately for the missing output schema.

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 the single schema description already says 'Opaque cursor from a previous next_cursor; omit once to bootstrap'. The description's guidance ('since=<next_cursor from your last call>', 'Omit since once to bootstrap') largely restates the schema, so 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?

States a specific verb+resource (delta of 8-K filings from /v1/edgar/events) and immediately scopes it as 'only the 8-K filings changed since your cursor'. The parenthetical '(delta of /v1/edgar/events)' makes the relationship to the full endpoint and to sibling tools unambiguous.

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?

Explicit operational contract: pass since=<next_cursor from your last call>, omit since once to bootstrap, and poll the free sibling /v1/edgar/events/changes for counts before paying. Names both the required flow and the cheaper alternative, so an agent knows exactly when to call this vs the sibling.

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