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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true and idempotentHint=false, so the safety profile is covered without the description. The description does add genuinely useful operational context not present in the annotations: the credit cost (100 credits, Tier 4) and the endpoint. However it never explains why a read-only operation is flagged non-idempotent (repeated calls likely yield differently worded narrative), which is the one behavioral trait an agent would most want here.

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 purpose sentence is front-loaded and the payload is small. The '[Required: planet1, planet2, aspectType]' line duplicates the schema's required array, but the cost and endpoint lines justify their space.

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 values need not be described. But for a 7-parameter tool with a nested chart object and LLM-backed generation, the description omits the valid domain for planet1/planet2, any usage guidance versus explain_transit, and any hint about generation latency or variable output.

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?

The description lists the three required parameters, but schema coverage is only 43% and planet1/planet2 carry no description, no enum and no example anywhere in the schema, so the agent must guess the accepted form (planet names such as 'Mars'?). The description does not compensate for that gap, which is the weakest part of the definition.

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 a specific verb and resource: 'explanation of an aspect between two planets.' An agent can tell it apart from the sibling astroway_mcp_ai_explain_transit by the resource alone, but the description never makes that contrast explicit nor states what kind of explanation is produced.

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?

There is no when-to-use guidance, no prerequisites, and no mention of the sibling explain_transit as an alternative. The only contextual cues are bracketed metadata (endpoint, required fields, credit cost), which tell the agent what it costs but not when it should be chosen.

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