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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and a closed (non-open-world) result set, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the substring match semantics ("protect" finds "protection") and a cost notice that the endpoint is not in the public credit manifest. It does not, however, describe result volume or pagination behavior, so it remains a moderate rather than rich disclosure.

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 short, front-loaded sentences: core behavior first, matching detail second. The bracketed Group/Cost metadata is boilerplate but carries an actionable cost caveat. 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 need not be explained, and annotations carry the safety profile. For a single-required-keyword lookup tool with full schema coverage, the description supplies everything an agent needs to call it correctly, including the matching rule and a cost pointer.

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%, so the schema already documents purpose, fields and precision, making 3 the baseline. The description reinforces the substring-match semantics of purpose (a subtle detail worth restating), but adds nothing about the fields/precision compact-mode parameters.

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 names a specific verb+resource combination (crystals indexed by purpose/intent keyword) and lists concrete example keywords, so the agent knows exactly what comes back. The name and text imply the distinction from sibling lookups like crystals_by_chakra and crystals_by_zodiac, but the description never names those alternatives explicitly, so it stops short of a 5.

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: reach for this tool when you have an intent keyword such as love or prosperity. However, there is no statement of when to prefer it over astroway_esoteric_crystals_recommend or the chakra/zodiac variants, and no exclusions or prerequisites. Adequate but with clear routing gaps.

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