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

Annotations only cover the read-only/idempotency profile; the description adds the costly operational facts an agent needs: tens-of-seconds latency with a >=90 s client timeout, 8 credits per call charged only on success, and a free sandbox key that returns a fixed sample. These are exactly the traits annotations cannot express.

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?

Front-loads the routing rule and then the cost/latency facts, and the example earns its space. However, latency is stated three separate times ('takes tens of seconds', 'set a client timeout of at least 90 s', 'allow up to 90 seconds'), which is redundant padding.

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?

An output schema exists, so return-value detail is not required, and cost/latency/routing are covered. The description is nearly complete, but the triple restatement of timing leaves it slightly less tight than it could 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?

Schema description coverage is 100%, so the baseline is 3; the description goes beyond that with a complete example argument object showing the birthData shape, a concrete domain value and question phrasing. It adds a worked invocation rather than restating field docs.

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?

Names a specific verb and resource ('written answer about what lies ahead in one area of life') and explicitly contrasts with the sibling interpret_domain ('for a fast, structured verdict use interpret_domain'). An agent can tell it apart from the structured-verdict tool without opening either 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?

Gives an explicit triggering condition ('when the user asks an open question about what lies ahead') plus the alternative route ('for a fast, structured verdict use interpret_domain'). Routing is fully determined by the description.

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