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

Annotations already declare readOnly/idempotent/non-destructive, so safety is covered. The description adds genuinely new context: a 10-credit Tier 1 cost and that results are top-N scored matches, neither of which appears in the structured fields.

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 tight sentences: purpose first, return shape second, with cost/group metadata clearly segregated. Front-loaded and no wasted prose.

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 needn't be detailed, and cost is disclosed. However, for a 7-parameter tool with 29% schema coverage and no usage routing, the description leaves the compact-mode parameters and the choice among crystal siblings unexplained.

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 only 29% (7 params, only fields and precision documented), so the description must compensate. It clarifies that sunSign/moonSign/ascendantSign are natal sign placements and intent is keyword-based, and 'top-N' implies limit, but it says nothing about compact mode (fields/precision) or valid sign formats.

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 (recommend) and resource (crystals) plus the scoring basis: natal Sun/Moon/Asc placements and intent keywords. This distinguishes it functionally from siblings like crystals_by_chakra and crystals_by_zodiac_sign, though it never names them 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 or when-not-to-use guidance, and no routing to the four sibling crystal tools. The agent must infer from the description that this is the multi-factor recommendation variant versus the single-filter siblings.

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