index_history_eod

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

With no annotations, the description must reveal behavior. It mentions the generation time (17:15 ET daily) and that it is free, but does not explain what an 'end-of-day report' contains, response format, or any refresh/delay implications. This is minimal behavioral disclosure.

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, front-loaded with '[FREE]', and every word adds value. It is appropriately terse for a simple data retrieval tool with no unnecessary 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?

Given the absence of an output schema, the description should explain what the 'end-of-day report' contains (e.g., OHLC, close-only) to set expectations. It does not, leaving the return value ambiguous. The tool is simple, but the description leaves a significant gap.

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 input schema has 100% description coverage for all three parameters, so the schema already explains symbol, start_date, and end_date. The description adds no parameter-specific semantics beyond this, matching the baseline for high coverage.

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 states 'End-of-day report for an index', which clearly identifies the tool's resource (index) and the type of data (EOD report). This distinguishes it from siblings like stock_history_eod and option_history_eod by specifying 'for an index', though it does not contrast with index_history_price or index_history_ohlc.

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 provides useful context: '[FREE]' signals cost, and 'Generated at 17:15 ET daily' tells when data becomes available. However, it does not explicitly state when to use this tool versus alternatives like index_history_price or index_history_ohlc, nor any exclusions.

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