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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds real value beyond that by spelling out the taxonomy of results (electromagnetic, companionship, dominance, compromise) and that it reports 'who holds what', which tells the agent what the response will look like. It does not mention failure behaviour for unresolvable birth places.

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 that opens with the verb and resource before enumerating results, with no filler. The parenthetical category definitions are dense but each one earns its place by clarifying an otherwise opaque term.

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 no output schema, the description takes on the job of describing the return value and does so thoroughly. For a nested 3-parameter tool it leaves the input side entirely to the schema, but the output side — the harder half — is well covered.

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 only 33% — the two nested person objects carry no top-level description — yet the description says nothing about the person inputs, language selection, or the noon/uncertainty fallback. All of that semantic detail lives in the nested schema, so the description does not compensate for the coverage gap.

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 and resource ('Compares two people's charts') and enumerates exactly what the answer contains: formed channels by category, combined chart type/definition/centres, and each person's Type, Authority and Profile. This is clearly distinguishable from get_chart, which handles a single person.

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 two-person scope implies when to reach for it instead of get_chart or get_transits, and the answer contents make the fit obvious. However, it never explicitly names a sibling or states a when-not condition, so the routing is inferred rather than declared.

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