market_list_markets

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

Beyond the annotations (readOnly, openWorld, idempotent, non-destructive), the description discloses experimental status, potential HTTP 500 failures, and instructs not to retry. It also adds the clarification that this is not the product category tree, providing further scope. This significantly enriches behavioral context without contradicting any 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 three sentences long, front-loaded with the primary action, and each sentence provides necessary information: purpose, experimental caution, and clarification. There is no redundant or filler content; every phrase 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?

Given the tool's simplicity (zero parameters, explicit output schema), the description covers all needed aspects: what it does, when to use it, how to handle errors, and what it is not. The output schema handles return values, so the description does not need to repeat that. The context is fully complete for an agent to decide when to invoke it and how to interpret results.

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 parameters, and the schema confirms this (coverage 100% trivially). Per the rubric, a baseline of 4 is appropriate when no parameters exist. The description does not need to explain parameters, and it correctly omits any parameter details.

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 explicitly states the verb and resource: 'List market chains via /api/v1/categories.' It further disambiguates from siblings by stating 'Not the product category tree,' which clearly distinguishes it from market_get_categories. The purpose is specific and unambiguous.

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 clear usage guidance: 'Optional, never a prerequisite for search or comparison.' It also specifies error-handling behavior ('On 500 report unknown chain active status and do not retry'), which tells the agent exactly what to do in a failure case. This is explicit and actionable.

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