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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds useful behavioral context beyond annotations by specifying the data scope ('19hz covers'), output format ('slug + label'), and domain focus ('electronic/dance music focus'). It does not contradict 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 two sentences: the first states the primary purpose and output, the second provides a usage note and domain context. Every sentence adds value, and the most critical information is front-loaded.

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 params, no output schema), the description is complete. It specifies the return value (slug + label), the coverage scope (19hz), the domain focus, and the relationship to the events tool, which fully covers what an agent needs to know to use this tool correctly.

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, so the baseline for parameter semantics is 4. The schema is empty and fully covered. The description adds no parameter details because none exist, but it does indicate that the output (slug) is used as an input to the events tool, adding related semantic context.

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 tool's function: 'List the regions 19hz covers (slug + label).' This uses a specific verb ('List'), identifies the resource ('regions 19hz covers'), and specifies the output fields ('slug + label'). It also distinguishes itself from siblings by noting it is a precursor to the events tool.

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 instruction 'Pass a slug to the events tool' provides clear usage guidance by explaining how the output connects to an alternative tool. However, it does not explicitly state when not to use this tool or contrast it with other region-related tools, so it lacks full exclusion guidance.

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