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

Annotations already cover safety (readOnlyHint, idempotentHint, destructiveHint=false), so the bar is lower. The description adds real value beyond them: it asserts deterministic (non-heuristic) calculation and documents an output convention — zero-based 0-11 sign index with a display-safe signName — which is not derivable from the annotations. It does not discuss compute cost, latency, or the timezone/timezoneOffset precedence, which is why it falls short of 5.

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?

Two sentences, no filler. The routing caveat is front-loaded in the first clause before the capability list, which is the right ordering for an expensive expert tool that should not be the default choice.

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?

An output schema exists, so return-value explanation is correctly omitted. However, for a 12-parameter, 6-required tool with 8% schema coverage and a three-way methodology enum, the description leaves too much to the schema — notably how to choose methodology and how timezone overrides timezoneOffset.

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 only 8% across 12 parameters, so the description must compensate for undocumented inputs, and it largely does not. It never explains focus, methodology, language, birthTimeAccuracyMinutes, or how timezone interacts with the required timezoneOffset — the one output-format note it gives concerns results, not inputs. The two sibling names give no parameter guidance.

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 names a specific verb (deterministically calculates) and enumerates the concrete outputs: sidereal placements, 16 Parashari vargas, Panchanga, Vimshottari timing, evidence and uncertainty. It also positions itself against two named siblings, so an agent can separate it from the large family of analyze_*/calculate_* tools without opening any schema.

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 gives an explicit routing rule: prefer consult_jyotishya or get_compact_chart_evidence for normal questions, implying this is the heavyweight full-matrix path. Both the when-not condition and the named alternatives are present, which is exactly what an agent needs to avoid over-calling an expensive tool.

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