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

With no annotations, the description carries the burden of behavioral disclosure. It adds valuable context: output content (counts and six strongest vs every active transit), token cost estimates (~800 vs ~4k), and default UTC time behavior. It doesn't cover edge cases or error behavior, but it transparently explains the main distinctions and expectations.

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 three short, front-loaded paragraphs. Every sentence earns its place: purpose, mode guidance with token costs, and default time behavior. No redundant or vague wording, making it efficient and 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?

Given the lack of annotations and low schema description coverage, the description provides enough context for correct tool selection and invocation: when to use, how to choose between modes, what output to expect, and the default date behavior. It doesn't detail every birth-data field, but those are conventional and have schema defaults. The output schema likely handles return structure, so the description is adequately complete.

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 low (20%), but the description compensates by explaining the mode enum, transit date parameters, and their default behavior. It also clarifies that the data object is birth data and warns about numeric month format. Nested birth-data fields are left to schema defaults, which is acceptable. This adds meaningful semantic value beyond the schema.

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: 'know what the sky is doing to a natal chart right now (or at a specific date)'. This is a specific, user-intent-oriented verb plus resource, and it distinguishes the tool from siblings like planetary_positions (positions without chart context) and transit_search (searching transits). The mode summary/full also reinforces the scope.

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 opens with 'Use when you want to...' and provides explicit mode selection guidance ('Call mode=full only when you need every active transit'), along with default behavior when transit_date fields are omitted. It gives clear context but does not name alternative sibling tools or state explicit exclusions, so it stays at a 4.

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