getHistoricalSP500Changes

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

Annotations already indicate readOnly and idempotent, and the description adds that the tool uses a specific API and returns change data. This does not contradict annotations, but the description does not reveal additional behavioral traits beyond what annotations provide, such as rate limits or data freshness.

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 very concise at two sentences, with no unnecessary words. The first sentence states the main action clearly, and the second adds context. Every word 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?

Given no parameters and annotations covering safety, the description is adequate but lacks details on the return structure (e.g., list of events with dates and companies). Without an output schema, more completeness would be beneficial for the agent to understand what data to expect.

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 no parameters, so schema coverage is 100%. The description does not need to add parameter meaning but mentions the specific API, which provides optional context. Baseline 4 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 clearly states the tool retrieves historical S&P 500 index data focusing on additions and removals of companies. It distinguishes from siblings like getHistoricalIndexFullChart (general index history) and getSP500Constituents (current list) by specifying 'changes' and using the 'Historical S&P 500 API'. However, it could be more explicit about the output format.

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 does not provide any guidance on when to use this tool over alternatives, such as when to use getHistoricalNasdaqChanges or getHistoricalDowJonesChanges. There is no mention of when not to use it, limiting the agent's ability to choose correctly.

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