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

Although annotations already declare readOnlyHint=true and idempotentHint=true, the description adds valuable behavioral context: results are machine-read from public filings, may contain errors, require source-link display, and must not be presented as personal investment advice. This goes well beyond the safety profile in the 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?

Two sentences carry a complete picture: the first front-loads the purpose and data fields, the second adds necessary caveats. 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?

For a parameter-less list tool with no output schema, the description covers the return contents, data provenance, and result-handling guidance. It could be slightly more explicit about any default ordering or result limits, but those are not critical for correct invocation.

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 tool takes zero parameters, so the baseline per the rubric is 4. The description correctly focuses on output semantics rather than input semantics, and there is nothing to compensate for in the schema.

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 resource ('Lists the large investors we follow'), then details the content (fund counts, newest move), source (SEC filings), and metadata (as-of dates, document links). It clearly differentiates itself from sibling tools like get_activist, which focuses on a single investor.

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 intended use is implied: call this when you want an overview of the large investors the system tracks. However, it does not explicitly contrast with alternatives such as get_activist (for a single investor) or list_events (for event-level data), nor does it state any exclusions or prerequisites.

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