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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds only that results are one-per-brand; it does not say what to expect for a user with no projects, whether the list is paginated or bounded, or what the call costs.

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, and the identity of the resource is front-loaded ahead of the routing hint. Nothing could be removed without losing 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 list tool with a clean schema and read-only annotations, this is nearly complete. The one real gap is the return shape: with no output schema, the agent isn't told which fields (e.g. an id vs. a display name) it should extract to feed the downstream projectId.

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?

Zero parameters, so there is nothing for the description to disambiguate; the baseline applies. The note about projectId being consumed elsewhere is useful framing but is not parameter semantics for this call.

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 ('Lists the user's Simplo projects') and adds a clarifying scope detail ('one per brand'), so the agent knows the granularity. It does not distinguish itself from the sibling list_accounts, which an agent must also disambiguate.

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 sentence 'Most other tools need a projectId from here' is an effective ordering signal that tells the agent to call this before other tools. It stops short of stating prerequisites or when-not-to-use conditions (e.g. when a projectId is already known).

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