list_sites

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

No annotations exist, so the description carries the full burden: it discloses the returned fields, the composite id format, that power values are in W, and that this is the discovery step for subsequent calls. It does not say whether the list is paginated, scoped to the authenticated account, or what happens with zero sites, which keeps it below a 5.

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?

Three short sentences: purpose first, return shape second, routing cue ("Start here.") last. No filler, no restatement of the tool name, and the most actionable cue is placed where it will be read.

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 listing tool with an output schema, the description covers purpose, key return fields, and downstream usage, which is enough to call it correctly. It leaves minor gaps on ordering, pagination, and empty-result behavior that an agent might want to know.

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 zero parameters, so the baseline is 4; there is nothing parameter-wise for the description to clarify. It spends its words on return-value semantics instead, which is the right allocation for a no-arg 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 specific verb and resource ("List the user's solar + battery sites across vendors") and additionally defines what a site record contains (id, vendor, name, online, headline power). The mention that the id is "vendor:station_id, used by every other tool" makes it distinguishable from the sibling get_site, which fetches a single site.

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?

"Start here." plus the note that the returned id feeds every other tool gives a clear entry-point condition and an implicit ordering against all siblings. It stops short of naming an explicit alternative (e.g. use get_site when you already have an id) or stating exclusions, so it is strong but not a 5.

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