Navaratna reference table

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

Annotations already declare readOnly/idempotent/non-destructive, so the description's contribution is the "static lookup, no chart needed" framing plus the 5-credit cost line, which is real behavioral context an agent can budget against. It adds nothing about response size or caching, but the annotations carry the safety profile.

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?

A single front-loaded sentence enumerating the catalog's fields, followed by terse group/endpoint/cost metadata. Dense but every clause maps to actual returned content; nothing is padding.

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 structure needn't be spelled out — yet the description still previews the fields, which is more than enough for a no-argument static lookup. An agent has everything needed to decide to call it and what it will get.

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?

Zero parameters, so the baseline is 4. The description correctly signals no input is required ("no chart needed"), which reinforces the empty schema rather than adding parameter detail there is none of.

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?

Names the resource (the nine Navaratna gems) and enumerates exactly what each entry carries — graha, upa-ratna substitutes, weekday, finger, metals, weight in ratti/gram/carat, beeja mantra and japa count. An agent can tell this is a static reference catalog, distinct from the chart-driven astroway_vedic_gemstones sibling, without opening the 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?

"Static lookup, no chart needed" gives a clear operational condition: call it with no birth data, as opposed to chart-based gemstone tools. It stops short of naming astroway_vedic_gemstones or astroway_reports_gemstone as the alternatives, so the routing is implied rather than explicit.

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