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

Annotations already declare readOnlyHint=true, idempotentHint=true, non-destructive and closed-world, so the safety profile is covered. The description adds value by disclosing what each entry carries (license and refresh cadence), but says nothing about ordering, pagination, or size of the returned set.

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?

A single sentence that front-loads the resource and appends the returned fields without filler. Every clause 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?

With zero parameters, no output schema, and full annotation coverage, the description supplies nearly everything needed: the subject data domain and the shape of each result (source, license, refresh). It only lacks detail on how the list is ordered or how large it may be.

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 takes no parameters, so schema coverage is moot and there is nothing for the description to disambiguate. Baseline 4 applies for a parameterless tool.

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?

States a concrete verb ('List') and a specific resource ('where the heat pump installer data comes from') and previews the per-source attributes returned. The resource is clearly distinct from the sibling list_* tools (categories, courses, places, products), though it does not explicitly name a sibling to contrast with.

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?

Usage is only implied: an agent can infer this is the discovery/provenance tool to call when it needs sourcing or licensing context. There is no explicit when-to-use vs when-not-to-use guidance and no mention of alternatives or prerequisites, but the zero-parameter nature leaves little room for misuse.

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