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

Beyond the annotations (readOnly, destructive, openWorld), the description discloses that the output is a fixed sample, not a live market run, and that it requires no authentication. It also lists exactly what data is returned, which adds significant behavioral context beyond the simple read-only hint.

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 well-structured and front-loaded: the first sentence states the main purpose and contents, the second clarifies the sample nature and contrasts with the paid subscription, and the third mentions cost and key requirements. Every sentence earns its place, with no redundancy.

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 tool with no parameters, read-only annotations, and no output schema, the description fully covers what an agent needs: what is returned, that it is a sample, and that it is free. There is no missing information required to call it correctly.

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 has zero parameters and the schema is empty (100% coverage), so there is nothing for the description to clarify about parameters. The baseline for a parameterless tool is 4, and the description adds no unnecessary parameter info.

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 states the tool's function: 'Get a real sample run of ValueFeed's Graham/Buffett-style value screen' and enumerates the specific metrics and excerpt returned. It distinguishes this from a live subscription by explicitly labeling it a 'fixed illustrative sample', so the agent understands exactly what it does.

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 implies usage by contrasting the sample with the paid weekly screen, and notes it is free with no key. It does not explicitly name sibling alternatives like get_valuefeed_info, but the context makes it clear this is for obtaining sample data rather than service information. A slightly more explicit routing to alternatives would warrant a 5.

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