ephemeris_next_lunar_phase

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

Despite strong annotations (readOnlyHint=true, idempotentHint=true, destructiveHint=false), the description adds behavioral details beyond annotations: the exact UTC datetime return, credit cost per occurrence (1-2 credits with explanation of why), and the search logic (second search when first window misses). It also clarifies default after_date behavior (today UTC) without contradicting the 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 somewhat long and uses emojis and sections, but it is well-structured and every element earns its place: purpose, usage rules, cost, and examples. It is front-loaded with the core function and immediately distinguishes from siblings, making it easy to scan.

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?

With no output schema, the description explains the return value ('exact UTC datetime'), covers all three parameters, provides usage boundaries, and includes cost behavior. It offers examples that demonstrate realistic invocation patterns, making it complete for a tool of this complexity.

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 baseline is 3. The schema already provides detailed descriptions for phase enum values, count range, and after_date format. The description contributes concrete usage examples, but these do not add new semantic meaning beyond what the schema already states.

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 opens with a specific verb and resource: 'Find the next occurrence of a specific Moon phase after a given date. Returns the exact UTC datetime of each occurrence.' It clearly distinguishes itself from the sibling ephemeris_moon_phase by explicitly stating what it is NOT for and pointing to the alternative.

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?

It provides explicit use cases with emoji-labeled sections: '✅ USE THIS TOOL FOR' and '❌ NOT FOR', and names the exact alternative tool for current phase/sign/degree questions. Multiple concrete examples (e.g., 'phase='new_moon'', 'after_date='2026-06-01'') further clarify when and how to invoke.

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