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

Annotations already establish read-only, open-world, non-destructive behavior. The description adds the useful 'Cost: 1 credit' disclosure and summarizes return content, but it does not cover auth, errors, or rate limits; with an output schema present, return-field prose is largely duplicate.

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?

The description is short, but it redundantly repeats the tool name ('Birthstones: Birthstones is...') and uses puffery ('comprehensive'). The cost note is the only high-value addition left at the end.

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 simple read-only lookup with four optional, fully documented parameters and an output schema, the description covers purpose and cost. It could say more about combining filters but is otherwise sufficient.

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 each of the four optional filters is documented in the schema. The description adds no parameter semantics or filter interaction guidance; baseline 3 applies.

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 states a specific verb-resource pair, 'lookup API for birthstone information,' and enumerates the returned fields. It does not name or differentiate a sibling such as ChineseZodiac or Horoscope, so it is clear but not fully sibling-aware.

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?

There is no explicit when-to-use guidance, no exclusions, and no indication of which of the four optional filters to choose. Only the implied reading that this is the birthstone lookup is available.

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