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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the agent knows this is a safe, non-mutating lookup. The description adds useful context about the source (FGAA-reviewed table) and the additional link to The Birthstone Handbook, which explains history and buying guidance. However, it does not disclose potential edge cases (e.g., invalid month handling, return format details) beyond what's in the schema. It adds moderate value without contradicting annotations.

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 concise: two sentences, with the core purpose front-loaded in the first sentence and the input flexibility in the second. Every word contributes to the agent's understanding of what the tool does and how to invoke it. No redundant jargon or filler.

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?

Given the tool's simplicity (one parameter, 100% schema coverage, and an output schema), the description covers the essential purpose. It mentions the source (FGAA table) and the linked handbook for further detail. It doesn't explicitly describe the return value structure, but the presence of an output schema likely covers that. The only minor gap is not specifying behavior for invalid months, but that's a minor edge case given the input examples.

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?

The schema describes the parameter 'month' with examples like 'September', 'sep', or '9', and it has 100% coverage. The description adds minimal semantic value by saying 'Accepts a month name or number.', which rephrases the schema's examples without providing additional format details (e.g., case-insensitivity, locale). Since the schema already documents the parameter thoroughly, the description's contribution is baseline-level.

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 clearly states the tool's purpose: it provides the modern and traditional birthstones for a month, based on a specific authoritative table (FGAA-reviewed), and includes a link for further information. It explicitly distinguishes its scope (month-based birthstone query) from sibling tools, even though it doesn't mention a sibling by name; the verb 'accepts' and the mention of month input clarify its function.

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 indicates when to use the tool: when you need birthstone information for a month. It does not explicitly exclude use cases or mention alternatives, but the context signals (e.g., sibling tools like 'gem_properties' or 'define_gem_term') imply that this is the dedicated birthstone tool. The lack of explicit 'when not to use' is a minor gap, but the specificity of the purpose provides sufficient guidance.

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