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

The annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so no contradiction exists. Beyond that, the description adds useful evaluation behavior: multi-line expressions with `let` bindings are supported, and the last expression is the result. This is meaningful behavioral context beyond the safety annotations.

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 compact and front-loaded: the first sentence states the core action, and the next two add expression vocabulary and syntax rules without fluff. It earns its length, though it could still have added param guidance without becoming bloated.

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 9 parameters, nested objects, enums, and no output schema, the description is not complete enough. It does not explain what the evaluation returns, what `reduce` modes mean, how `parameters` maps into the expression, or how `includeForming` affects behavior. For a tool of this complexity, this is 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?

Schema description coverage is only 44%, so the description must compensate, but it only clarifies the `expression` parameter via series names and `let` bindings. Parameters like `reduce`, `includeForming`, `parameters`, `exchange`, and `ref` remain unexplained in both schema and description, leaving a substantial semantic gap.

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 clearly states the operation: 'Evaluate a Basis formula expression over a loaded window.' It names the expression domain, mentions available series (open, high, low, close, volume, returns), and points to catalog_search for function discovery. However, it does not explicitly differentiate itself from siblings like indicator_compute or market_candles.

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 implies the tool is used when a formula needs to run over an already-loaded window and points to catalog_search for valid expressions, which gives context. It never states when not to use it or names alternatives, so the guidance remains implicit and partial.

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