add_child_to_family

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

Annotations already declare the mutation profile (readOnly=false, destructive=false, openWorld=false), so the description earns credit for going beyond them by explaining the bidirectional side effect (ChildRef on the family plus the family added to the child's parent-family list) and the duplicate-handling rule. The 'duplicate children are skipped' wording sits in mild tension with idempotentHint=false, but it reads as a data-integrity rule rather than a claim of full operation idempotency, so it is not a hard contradiction.

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 core action is front-loaded in the first sentence, with side effects and preconditions following in short supporting sentences. It is tight overall, with only a small amount of wordiness in the 'Links the child both ways' sentence.

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 4-parameter mutation tool with full schema coverage and no output schema, the description covers what is created, the precondition, and duplicate handling. Error behavior (e.g., nonexistent family/child) and permission requirements are unstated, but those gaps are minor.

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?

Schema description coverage is 100%, so the schema already documents family, child, frel, and mrel with examples. The description adds only the 'child must already exist' constraint and implies the family must pre-exist; it adds no format or value details for the two relationship parameters beyond what the schema provides.

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 gives a specific verb (Add) and resource (an existing person as a child of an existing family) that is unmistakably distinct from sibling tools like add_person, add_family, add_event_to_family, or link_repository. An agent can identify the operation without opening the schema.

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?

It supplies an important precondition ('The child must already exist'), which tells the agent to create the person first via add_person rather than passing new data. However, it never states when to choose this tool over alternatives or explicitly rules any sibling in/out, so usage guidance remains implied.

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