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

Annotations already mark readOnly, idempotent, open-world, and non-destructive, so the bar is lower. The description adds useful behavioral content by stating the result is free and by disclosing exactly what the payload includes: ticker format, segment membership lists, and methodology version. There is no contradiction with 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?

Three short sentences with no filler; the cost note is front-loaded, followed by scope, concrete examples, and included artifacts. Every 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?

For a zero-parameter read-only reference endpoint, the description covers the essential output contents and naming scheme. Since no output schema exists, the description's enumeration (tickers, segment, definition, membership lists, methodology version) serves as the primary documentation and is sufficient for an agent to call and interpret the tool.

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 schema has zero parameters, so the baseline is 4. The description adds useful meaning for interpreting returned data by defining ticker syntax (CX.<MODEL>.<SEGMENT> and CX.<MODEL>.SPOT.<REGION>), even though no parameters exist to document.

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 identifies the resource ('every index ticker') and enumerates the returned content: segment, definition, ticker format, membership lists, and methodology version. 'Every' plus the naming convention makes its scope clear, distinguishing it from the index_history and index_board siblings. The implicit verb 'returns/lists' is obvious from context.

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?

It implies a reference use case: use this when you need the full catalog of index ticker codes, their segments/definitions, or methodology version. It does not explicitly name sibling alternatives or state when not to use this tool, such as for historical index data. The 'Free' note hints at cost considerations but not invocation context.

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