Market data: major market indices

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

With no annotations, the description carries the behavioral burden and does well: it discloses dual sourcing from Finviz and TradingView/Yahoo, explains ticker normalization to canonical names, and notes that each result carries its own data_provider. It does not mention latency, caching, rate limits, or failure behavior, but the core data provenance and comparison behavior are transparent.

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 front-loaded with the purpose, then the covered indices, then the normalization behavior, then the return shape. Every sentence adds useful information and there is no redundant wording.

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?

The tool is simple, parameterless, and has an output schema, so the description is nearly complete: it covers scope, sources, canonical keys, and returned fields. It could add update frequency or freshness expectations, but no critical invocation detail is missing.

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 input parameters, so the baseline is 4. There are no parameter semantics to explain beyond the absence of arguments.

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 a specific resource and payload: dual-sourced level and day change for major US indices, explicitly listing S&P 500, Dow, Nasdaq Composite, Russell 2000, and VIX. It is clear what the tool returns, though it does not explicitly differentiate itself from siblings such as market_snapshot or futures_market_overview.

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?

Usage is implied by the listed US indices and day-change scope, which tells an agent this is for broad US index levels rather than individual stocks or futures. However, there is no explicit when-to-use guidance, no prerequisites, and no named alternative for overlapping snapshot or sentiment tools.

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