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

No annotations are provided, so the description carries the full behavioral burden. The verb 'List' and the word 'Discovery' imply a read-only, non-mutating operation, but the description does not explicitly state that there are no side effects, whether authentication is needed, or what kind of output shape is returned. These are minor gaps for a simple discovery tool, but the description could be more explicit.

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 short sentences with no filler. The main action and resource are front-loaded, and the second sentence adds the discovery purpose. Every word 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 discovery tool with no output schema, the description adequately conveys what the tool lists and why an agent would use it. It does not spell out the exact return structure, but the categories mentioned ('data sources, dimensions, metrics, and operations') give enough context for an agent to understand what to expect.

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 coverage is 100% trivially, since there is no property surface to document. The baseline for 0 parameters is 4, and the description correctly focuses on the output categories rather than trying to explain non-existent parameters.

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 states a specific verb ('List'), a concrete resource ('Fusion Engine data sources, dimensions, metrics, and operations'), and the purpose of the tool ('Discovery tool for understanding what cross-source queries are possible'). This clearly distinguishes it from the sibling query tools by identifying it as a meta/capability tool rather than a data retrieval 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 description frames the tool as a 'Discovery tool for understanding what cross-source queries are possible,' which clearly implies using it when planning or choosing what queries to run. It does not explicitly name alternatives or state when not to use it, but the context is strong enough for an agent to infer appropriate usage.

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