Inspect historical timezone and DST

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

With no annotations, the description carries the full burden of behavioral disclosure. It clearly states the operation is a read/computation: resolving to UTC and reporting DST status. It also discloses a key behavioral nuance—it uses historical rules and avoids the present-day offset that causes wrong charts. It does not detail the exact return shape, but the 'report whether...' phrasing gives a solid implicit contract.

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 core purpose is front-loaded in the first sentence, and the additional historical examples are purposeful rather than filler. It is slightly verbose with the DST period list, but that content directly supports why the tool matters and when to use it.

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 tool with no output schema and no annotations, the description covers what the tool does, why it is needed, and the common pitfall it avoids. It does not explicitly state the output format or edge cases like invalid dates during DST transitions, but it gives enough behavioral context for an agent to call it correctly and interpret its purpose.

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 baseline is 3. The description adds contextual value around the timezone parameter by explaining historical DST relevance and the birthplace-vs-user distinction, but it does not add parameter-level syntax or format details beyond what the schema already provides.

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 and resource: 'Resolve a local birth date and time to UTC using historical timezone rules' and 'report whether daylight saving time was actually in effect.' It distinguishes itself from chart-generation siblings by framing itself as the explanation for why charts differ, not as a chart calculator.

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 gives an explicit usage directive: 'Use this to explain WHY two charts differ.' It also provides concrete historical DST windows and warns against the common present-day-offset mistake, giving strong contextual cues for when this tool is appropriate. However, it does not explicitly contrast with sibling tools like calculate_natal_chart or verify_ascendant, so exclusions are implied rather than stated.

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