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 clearly indicates a read-only listing operation ('List all'), but it does not describe the output format, size limits, or any prerequisites. This is minimally sufficient but not rich.

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?

Two sentences, no filler. The first names the action and scope, and the second adds the discovery purpose. Every clause contributes useful decision information.

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 discovery list, the description covers what it lists and why to use it. It does not specify the return structure, but for a capabilities endpoint this is largely inferable. It is complete enough for correct invocation while leaving minor room for extra detail.

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 description cannot add parameter-level meaning. The baseline for zero-parameter tools is 4, and the description appropriately focuses on what the tool returns rather than input configuration.

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 uses a specific verb ('List') and names the exact resources covered ('Fusion Engine data sources, dimensions, metrics, and operations'). It also identifies itself as a 'Discovery tool', making its introspective role clear and distinguishing it from the sibling query/action tools.

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 phrase 'Discovery tool for understanding what cross-source queries are possible' gives clear context for when to use it: before constructing cross-source queries. However, it does not explicitly state when not to use it or name alternative tools, leaving some inference to the agent.

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