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

With no annotations provided, the description carries the full burden of behavioral disclosure. It states 'Pure static data, always returns 200, no authentication required, sub-50ms p95' and notes the tool is 'model-agnostic.' These details go beyond what any structured field provides and give the agent confidence about safety, performance, and side-effect-free behavior.

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 core purpose and return type, and it uses clear section labels (WHEN TO USE, RETURNS). The exhaustive list of 28 exchanges with MIC codes is informative for a directory tool, but it is longer than strictly necessary and partially duplicates what the tool itself returns. Still, every section serves a distinct purpose.

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 description provides the return shape inline, including the nested object structure and mic_type enum values. It also covers usage timing, coverage scope across equities/derivatives/crypto, and behavioral guarantees (200, no auth, p95). For a read-only discovery tool with no annotations and no output schema, this is fully sufficient 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 tool has 0 parameters, so the baseline is 4. The description appropriately spends no space on parameters and instead details the output shape. No parameter ambiguity exists, and the schema confirms no inputs are required.

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 opens with a specific verb and resource: 'Returns directory of all 28 exchanges supported by Headless Oracle.' It enumerates the exact content fields (MIC codes, exchange names, IANA timezones, market hours metadata, mic_type) and distinguishes the tool from siblings by explicitly referencing get_market_status and get_market_schedule later.

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 'WHEN TO USE' section is explicit: 'call once at agent startup to discover supported markets before calling get_market_status or get_market_schedule.' It gives clear timing, purpose, and names the sibling tools it precedes. This leaves no ambiguity about when to select this tool.

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