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

Annotations already convey read-only, non-destructive behavior, so the description only needed to add behavioral context. It does so by specifying that all chart points are computed as midpoints and by stating the invariant that the Ascendant sits on the first cusp, which usefully signals the exact calculation approach.

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 first several sentences earn their place by explaining the method, result, and return contents. However, the final sentence is a loose keyword list ('Composite chart API, midpoint relationship calculator, relationship astrology, couple chart analysis') that adds no functional guidance for an agent and slightly dilutes an otherwise clear description.

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?

The description lists the principal returned components: planetary positions, house cusps, Ascendant, Midheaven, aspects, and relationship interpretation. Since no output schema exists, this return summary is valuable. Combined with the rich parameter schema and read-only annotations, an agent has sufficient context to select and invoke the tool.

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 every parameter already has a rich description including defaults, formats, and examples. The tool description adds little parameter-level detail beyond referring generally to two natal charts and the midpoint method, so it does not significantly exceed what the schema already 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 clearly states a specific action ('Generate') on a specific resource ('composite chart') and gives the midpoint method. It also distinguishes this tool from synastry/compatibility siblings by emphasizing that the composite chart represents the relationship as a single entity rather than comparing two charts.

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 description gives clear context for when to use the tool: whenever a midpoint-based relationship chart is needed. It does not explicitly name alternatives or say 'use this instead of synastry', so it falls short of full routing guidance, but the semantic distinction between relationship-as-a-single-entity and other relationship chart types is effectively implied.

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