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

Without annotations, the description discloses useful behavioral details: data is pre-computed every 15 minutes and stored since v2 launch (2026-04-09). This communicates freshness and availability bounds. It also describes the data as 'snapshots', implying point-in-time readings, which adds context beyond the schema.

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?

Three short sentences covering resource, update cadence, data history start, and use case. No filler or 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 one optional parameter and no output schema, the description covers the core purpose, data timing, storage start, and intended use. It is sufficient, though it could explicitly mention that data is limited to the SimpleFunctions Index, which is already implied by the tool name and first sentence.

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 only parameter 'days' is fully documented in the schema with type and default (7). The description adds no extra parameter-specific meaning, but the schema fully covers it, so a baseline score 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?

The description identifies the resource as 'Historical SimpleFunctions Index snapshots', making it clear the tool retrieves historical index data. It distinguishes by naming the specific index, though it lacks an explicit verb or direct comparison to sibling history tools.

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?

States the intended use case ('For charting trends'), providing implicit context for when to use it. However, it does not mention alternatives or exclusions relative to sibling tools like get_market_history or get_evaluation_history.

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