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

Annotations already cover read-only, idempotent, non-destructive, open-world, so the description is free to add real behavioral context: the five-year window, weekly closes, dividend/split adjustment, and the full returned metric set including fee for funds. The "covered" qualifier also warns about instrument coverage limits, which is not in any structured field.

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 scope and window, then the metric list, then usage examples — a sensible order. The metric enumeration is long and partly duplicates the output schema, so a sentence could be trimmed, but nothing is genuinely wasted.

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?

With an output schema, fully described params, and rich annotations, the remaining burden is methodology and scope, both of which are covered (weekly closes, dividend/split adjustment, five-year horizon, coverage restriction). An agent can call this correctly without opening anything else.

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 coverage is 100% for both tickers, so the schema carries the syntax and examples. The description adds the meaningful constraint that inputs must be covered stocks or ETFs and shows a matched pair per asset class, which is more than restating the schema.

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+resource+scope: a five-year head-to-head of exactly two tickers, with the exact metric set enumerated. It is clearly distinct from single-ticker siblings like analyze_ticker or fund_fees because the two-input comparison is stated up front.

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 closing line gives concrete triggering phrasings ("SCHD vs VIG", "NVDA vs AMD") and the description scopes inputs to "covered" stocks or ETFs. It stops short of naming alternatives or stating when not to use it (e.g., one ticker → analyze_ticker, overlapping ETFs → etf_overlap).

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