Retrieve historical S&P 500 index changes, including company additions and removals, to analyze trends and performance over time.
Retrieve historical data for the S&P 500 index using the Historical S&P 500 API. Analyze past changes in the index, including additions and removals of companies, to understand trends and performance over time.
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
v2.9.0Input schema / $schemaPrevious value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"v1.0.0Input schema / additionalPropertiesRemoved value: -falseDoes the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the safety profile is covered. The description adds useful context that the tool focuses on additions and removals of companies, but it does not describe return format, date coverage, or whether results are paginated.
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 two sentences and front-loads the retrieval purpose. The second sentence is useful but includes somewhat generic phrasing about understanding trends and performance over time, which slightly reduces precision.
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 zero-parameter historical retrieval tool with no output schema, the description adequately states the subject matter and that changes include additions and removals. However, it does not clarify the return shape or temporal scope, which would help an agent understand what historical 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 zero parameters, so there are no parameter semantics to document. Per the rubric, zero parameters sets a baseline of 4.
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 that the tool retrieves historical S&P 500 data and specifically mentions additions and removals of companies. It is distinguishable from siblings like getSP500Constituents, but it does not explicitly contrast itself with related tools such as getHistoricalNasdaqChanges or getHistoricalDowJonesChanges.
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 the tool is for analyzing historical index changes, but it provides no explicit when-to-use guidance, prerequisites, or alternatives. It does not tell an agent when to choose this over sibling tools like getSP500Constituents or the Nasdaq/Dow Jones historical change tools.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.