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

The annotations already declare a safe, read-only, idempotent, closed-world lookup, so the description's main added value is the disclosure of what data is returned (page locator, Karmic Condition/Focus/Quest neighbours, handling, water, price, availability) and the caveat that a 'safe stand-in' is substituted where data is missing — a genuine data-quality disclosure. It stops short of describing any limits on the lookup, but with full annotation coverage the bar is lower.

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 sentences, front-loaded with the lookup modes and then the return payload; nothing is filler. The return enumeration is slightly heavy given an output schema exists, but it is compressed and each item is a distinct data point.

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?

For a one-parameter lookup with an output schema and full annotation coverage, the definition covers input modes, output shape, and a data-quality caveat, so an agent can invoke it correctly. It is not fully complete on routing — nothing tells the agent how this differs from the crystal-calculation siblings — which is the main remaining 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 the baseline is 3, but the description adds real meaning beyond the schema: it explains that the number maps to the book's astrological numerology (house or street number), gives a concrete degree syntax example, and notes the name alternative. The single parameter's accepted forms and their intent are clearer than the schema text alone.

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 gives a specific verb and resource ('Looks up Costelloe's crystal astrology table') and enumerates the three accepted key types with an example ('number 1-360 ... e.g. a house or street number', '"Libra 2"', 'crystal name'). It is clearly a reference-table lookup rather than a computation, which implicitly separates it from siblings such as calculate_crystal_profile or calculate_crystal_timing, though no sibling is named outright.

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?

Usage is implied through the accepted query forms — an agent can infer it should call this when it already has a crystal number, degree, or name. However, there is no explicit guidance on when to prefer calculate_crystal_profile or calculate_crystal_timing instead, and no preconditions or exclusions are stated.

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