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

With no annotations, the description carries full burden. It describes the sweep as non-destructive computation (generating ASC/MC values), implying read-only behavior. It explains the algorithm (step across hours, window constraints) but does not explicitly state it does not modify data or require auth. Given the tool's nature, this is adequate.

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 two sentences, front-loading purpose and usage in the first sentence, and parameter behavior in the second. No filler or repetition.

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 6 parameters, no output schema, and no annotations, the description is fairly complete. It explains the sweep mechanism, parameter roles, and hints at output (ASC/MC values, sign-change times). It could briefly mention the output format, but given the tool's simplicity, it suffices.

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 coverage is 100%, so baseline is 3. The description adds value by explaining that 'window_start_hour' and 'window_end_hour' are UTC hours of the given date, that 'step_minutes' controls grid spacing, and that the date's time portion is ignored. This goes beyond the schema descriptions.

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 it performs a 'rectification sweep' producing ASC/MC values and sign-change times across a window of UTC hours on a single date. It explicitly distinguishes the use case: 'Use when the birth time is unknown and you want candidate times.' This differentiates it from sibling tools like 'natal_chart' or 'transits' which do not focus on unknown birth times.

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 explicitly directs when to use the tool: 'Use when the birth time is unknown and you want candidate times.' It does not specify when not to use or mention alternatives, but the use case is clear and unique among siblings, which provides sufficient guidance for an agent.

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