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

Annotations already declare readOnlyHint=true and destructiveHint=false, establishing it as a safe read operation. The description adds valuable behavioral context by specifying the access scope ('owned + shared'), which clarifies what 'has access to' means. No contradictions with annotations.

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?

The description is a single concise sentence, front-loaded with the main action ('List all babies') followed by the scope clarification. Every word earns its place with no redundancy or filler.

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 simple list operation with no parameters and an existing output schema, the description is complete. It states the resource and access scope, and the output schema covers return value structure. There is no missing information that would prevent correct tool invocation.

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 input schema is empty, so there are no parameter semantics to explain. With 0 params, the baseline is 4, and the description doesn't need to add anything further.

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 clearly states the tool's purpose: 'List all babies the user has access to (owned + shared).' The verb 'list' is specific, the resource 'babies' is explicit, and the scope 'owned + shared' distinguishes it from single-baby retrieval tools like get_baby and other list tools (list_diary, list_feeds, etc.).

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 provides clear context on when to use the tool: when the goal is to retrieve all accessible babies, including both owned and shared. It doesn't explicitly mention alternatives or exclusions, but the phrase 'all babies the user has access to' implies it is for collection-level retrieval, differentiating it implicitly from get_baby.

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