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

Annotations already declare readOnly, idempotent and non-destructive, so the bar is lower; the description still adds real value by naming the data source (Yahoo Finance via yfinance), stating no API key is needed, and describing the flattened column-naming convention. It omits failure behavior for bad tickers, alignment of differing trading calendars, and result-size limits.

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?

Front-loaded with the core action and output shape before the scenario bullets, with no filler sentences. The three 'use when' bullets partially overlap (relative performance / correlation matrices are near-synonyms), so it is slightly longer than strictly needed.

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?

An output schema exists and annotations cover the safety profile, so the description needn't explain returns. However, the schema exposes several confusing fields irrelevant to price history (wholesaler_ids, exclude_fillers, mcp_prompt_id, question_asked) that the description never addresses, and there is no guidance on symbol limits or invalid-ticker handling.

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?

Schema description coverage is reported at 0% (the top-level 'params' ref has no description), so the description should carry more of the parameter burden. It only explains the 'symbols' delimiter format, which the nested schema already states verbatim, and says nothing about start/end vs. period precedence or interval choices — despite this being a one-argument wrapper over a large nested object containing several unrelated-looking fields.

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 opening sentence gives a specific verb and resource ('Fetch OHLCV price history') plus the distinguishing scope ('for multiple tickers in a single call'), and even sketches the flattened output shape ('AAPL_Close', 'SPY_Volume'). It never names the obvious sibling GetPriceHistory, so the agent must infer the single-vs-multi split from the scope wording alone.

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?

A dedicated 'Use this tool when' block gives three concrete scenarios (cross-security comparison, portfolio correlation, relative performance), which is clear positive guidance. It stops short of when-not guidance and never routes the agent to GetPriceHistory for a single ticker or notes any ticker-count limits.

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