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 fully covered. The description adds the output shape (top-3 emphasized houses per side), but that is also captured by the output schema. It adds little behavioral context beyond structured data.

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?

Single front-loaded sentence describing the operation, followed by a compact metadata block (group, endpoint, required, cost). No filler. Slightly longer than strictly necessary because the metadata partly duplicates the schema's required list.

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?

With a full output schema and complete annotations, the description need not explain returns. What is missing is positional context: with ~30 relational siblings, an agent needs a sentence on when this overlay is the right choice versus aspect-grid or composite variants. Otherwise it is adequate for calling the tool correctly.

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 chart1/chart2 are richly documented inline (timezone handling, house system letters, rejected short forms). The description adds nothing about parameters, so the baseline 3 applies — the schema does all the work.

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 concrete verb and resource: placing each chart's personal planets in the partner's houses and reporting the top-3 emphasized houses on either side. That is specific and unambiguous. It does not, however, distinguish itself from the dense set of sibling relational tools (synastry_aspect_grid, synastry_attraction_score, synastry_element_balance, composite, davison).

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?

No when-to-use or when-not-to-use guidance. The metadata block lists required inputs and cost but never says how this differs from astroway_relational_synastry, astroway_relational_synastry_aspect_grid, or astroway_relational_composite, which is exactly the decision an agent must make in this crowded group.

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