Market depth exchanges

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

Annotations already declare readOnlyHint and openWorldHint, so the description only needs to add context. It does so by stating 'The list is static and cached for the gateway session' and 'this list does not' subscribe to depth. This helps the agent understand the data is not live and the tool has no side effects beyond returning a cached list.

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 two tight sentences. The first sentence delivers the core purpose. The second adds field details, usage timing, the subscription distinction, and caching behavior—all without waste. Information is front-loaded and each sentence earns its place.

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 zero parameters, a defined output schema, and readOnly/openWorld annotations, the description covers all essential context: what the tool returns, the fields in each row, when to use it, and its static/cached nature. No critical details are missing for correct invocation.

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 input schema has zero parameters, so the baseline is 4. No parameter explanation is needed, and the description correctly avoids inventing any. The description's field-level details (exchange, security type, listing exchange, depth service type) apply to the output, which the output schema covers.

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 begins with a specific action and resource: 'List the exchanges that offer market depth (level 2 order book), per security type.' It clearly differentiates from subscription tools by framing itself as a reference list to consult before subscribing. The title and description align without tautology.

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 provides explicit when-to-use guidance: 'Check it before subscribing to market depth.' It also clarifies what this tool does not do: 'Depth itself needs a separate depth data subscription at IBKR; this list does not.' It implies the alternative (subscribe_market_depth) but does not name it explicitly, so it falls just short of a 5.

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