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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and closed-world, so the safety profile is covered. The description adds genuinely new behavioral context not present in structured fields: the HTTP endpoint and the cost of 10 credits at Tier 1, which matters for budget-aware agents. It says nothing further about latency, output shape, or limitations.

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?

One sentence plus four compact metadata lines, front-loaded with the purpose. Nothing is padded, though the 'Required' line duplicates what the schema already enforces, so it is not quite maximally lean.

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 two-chart synastry tool with nested birth objects, an output schema, and many close siblings, the description is minimally adequate. Because an output schema exists, return values need not be explained, but the 'deep' qualifier is never contrasted with any shallower or alternative family analysis, leaving the agent without routing context.

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% and the nested birth-data objects carry extensive inline documentation (coordinate rules, timezone behavior, houseSystem letters). The description only repeats the two required parameter names already declared in the schema, adding no semantics of its own. Baseline 3 is appropriate when the schema does the heavy lifting.

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 states a specific verb and resource: 'Deep parent-child synastry analysis.' Adding 'synastry' tells the agent this is a two-chart comparison rather than a single natal read, which is more than the name alone conveys. However, it does not distinguish this from sibling family tools such as astroway_family_system_pattern, astroway_family_sibling_dynamics, or the relational synastry tools, so the boundary is left to inference.

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 only routing information is the bracketed metadata block: group, endpoint, required params, and cost. There is no statement of when to choose this over the other family or relational synastry tools, and no exclusions or prerequisites. The agent must infer usage entirely from the name.

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