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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the description's job is lighter. It adds real context beyond that: the upstream source (Yahoo Finance via yfinance), that no API key is needed, and the breadth of coverage across asset classes. It does not say how invalid/unknown symbols behave or whether results are cached or rate-limited.

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 return payload, then use-cases, then supported symbol formats — a sensible ordering for an agent scanning it. The symbol-format list slightly duplicates the schema's symbol description, but the overall length is proportionate.

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, so the description need not explain return values, and what it does say about coverage is adequate. However, the input schema exposes a set of unrelated filter/context parameters that the description neither explains nor dismisses, leaving ambiguity about what actually must be supplied.

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 effectively 0% at the top level (a single 'params' object), and the nested schema carries unrelated fin-domain parameters (wholesaler_ids, exclude_fillers, source_resource_id, mcp_prompt_id) that the description never mentions. The description does compensate for the main 'symbol' argument by enumerating accepted formats for stocks, ETFs, funds, crypto, indices and forex, but it leaves the rest of the parameter surface unexplained.

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?

States a specific verb and resource ('Fetch the full Yahoo Finance profile') and enumerates the returned fields (sector, market cap, P/E, 52-week range, beta), so the agent knows exactly what this returns versus a price-history or holdings tool. It does not explicitly differentiate from nearby siblings like LookupTicker or GetFundProfile, which keeps it from a 5.

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 'Use this tool when' block gives three concrete triggers (company/fund summary, sector/industry classification, market cap/float/short ratio metadata), which is clear positive guidance. It offers no exclusions or pointer to alternatives (e.g. when to use LookupTicker for symbol resolution instead).

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