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

Annotations already indicate read-only, idempotent, and non-destructive behavior, and the description adds substantial context beyond that: calibration against Jagannatha Hora, English-only names regardless of language settings, the civil-midnight meaning of epoch.vaara, no side effects on other tools, and 'Data only — no verdict.' These are non-obvious behaviors an agent needs to know.

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?

Three dense, purposeful sentences. The first front-loads the main purpose and output contents; the second adds calibration and scope; the third resolves naming/epoch ambiguity and the no-verdict caveat. Every sentence earns its place with no filler or redundancy.

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 carries full responsibility for explaining return values, and it does so thoroughly: nine bodies with sign/degree/nakshatra/daily motion/sighra-kendra/retrograde flag, SS lagna, SS ayanamsa with delta, and SS panchanga details. It also clarifies naming, weekday semantics, and the non-verdict nature of the data, covering everything needed to select and call the tool correctly.

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 parameters themselves are already fully documented with formats, examples, and optionality. The tool description adds no per-parameter semantics beyond the schema; it only summarizes the output contents. Baseline 3 is appropriate because the schema already carries the parameter documentation burden.

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-resource pair: 'Classical Surya Siddhanta ... D-1 positions for a birth instant,' enumerating exactly what is computed. It distinguishes itself from siblings by explicitly stating that every other tool stays Drik, so an agent can tell this tool apart without opening schemas.

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 clearly signals when to use this tool: when Surya Siddhanta positions are needed, because 'Every other tool stays Drik, and this tool does not change them.' It also adds 'Data only — no verdict,' which tells the agent not to use it for interpretive output. It stops short of naming a specific sibling alternative for Drik charts, so it is slightly less explicit than the highest bar.

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