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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds genuine extra context: the 50-credit Tier 3 cost and the required parameters. However it says nothing about output shape or what the composite is useful for, so it only partially extends 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?

A single front-loaded sentence states the operation and method, followed by compact bracketed metadata (group, endpoint, required, cost). No filler, though the bracketed block is terse rather than prose and the whole thing is quite sparse.

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 rich output schema and full annotations, the description carries a light load, and it does supply method, cost, and required inputs. The one real gap is the absence of any sibling differentiation among the many relational comparison tools, which the agent would need to choose 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%, so the nested chart1/chart2 objects and the fields/precision compact-mode parameters are already fully documented in the schema. The description only repeats the two required params, adding no meaning beyond the schema.

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 specific verb (Calculate) and resource (midpoint composite chart) and explains the method — averaging planetary positions and house cusps of two natal charts. This implicitly distinguishes it from the Davison sibling (a different composite method), though it never names any sibling explicitly.

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 guidance is given. Nothing tells the agent when to pick a midpoint composite over astroway_relational_davison, astroway_relational_synastry, or astroway_relational_coalescent. The only routing help is the structural [Group: Comparisons] tag.

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