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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world). The description adds real behavioral context beyond that: Earth replaces the Sun, the Moon is excluded, and the call costs 20 credits at Tier 2. Return format is not described, but an output schema exists to cover it.

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?

Front-loaded with the core purpose in the first sentence, then compact bracketed metadata (group, endpoint, required, cost) that is scannable and wastes no words. Slightly dense but well organized.

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 15-parameter chart endpoint with an output schema, the description supplies purpose, the key astronomical edge cases, cost, endpoint, and required inputs. The main remaining gap is the absence of any sibling differentiation among the specialized chart family.

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 33%, so the description should compensate for undocumented parameters, but it only restates the four required fields (date, time, latitude, longitude) that the schema's required array already lists. It adds no meaning for the many other parameters (houseSystem, zodiacType, ayanamsaId, cosmogram, etc.).

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?

States a specific verb and resource ('Calculate heliocentric planetary positions'), clarifies the frame with '(Sun-centered)', and adds distinguishing edge behavior ('Earth replaces Sun; Moon is excluded'). It does not, however, differentiate itself from sibling specialized charts (draconic, harmonics, horizon, vedic_divisional), so an agent must infer the boundary.

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 phrase 'for a given birth moment' hints at input context but there is no explicit when-to-use, when-not-to-use, or named alternative. Given a cluster of specialized chart siblings, the agent is left to guess which chart type is appropriate.

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