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

Annotations already cover the safety profile (readOnly, idempotent, closed-world), so the description's added value is the 'free', 'no predictions', and 'no personal data stored' disclosure plus the deterministic date-table method. That meaningfully extends beyond the annotations, though it does not spell out caching or output delivery behavior.

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?

Two tightly packed sentences with zero filler; the scope and content of the return are front-loaded, and the privacy/scope limits follow immediately.

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?

An output schema exists, so return values need no explanation, and the description adequately scopes inputs and limits for this simple read tool. Only the routing versus sibling tools remains unaddressed, which is a minor gap.

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 coverage is 100%, so both parameters (birth_date, language) are already fully documented including format and default. The description only restates that a birth date is the sole input and that time/place are unnecessary, which is already in the schema text, so it adds little beyond the baseline.

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 (Returns) and resource (short, free reading), and enumerates exactly what it contains: sun sign from a date table plus a Pythagorean life path number with character text. The 'based only on a birth date' framing implicitly separates it from the heavier get_birth_chart sibling, but no sibling is named 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?

The description makes the use case inferable (a lightweight, no-birth-time reading) and rules out prediction use, but it never says when to pick this over get_birth_chart, compare_charts, or get_transits. Usage is implied rather than directed.

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