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

Annotations declare readOnlyHint=false, idempotentHint=false and openWorldHint=true, so the write-ish, non-idempotent, live-data character is already signaled. The description adds useful context the annotations lack — that this is a Real-time Streaming tool and that it costs 10 credits (Tier 1) — but says nothing about stream duration, termination, or what triggers an update, which matters for a streaming endpoint.

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 and kept to a single content sentence plus two bracketed metadata tags. Nothing is wasted, though the metadata lines are formatting rather than explanation.

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 no explanation, and the cost/streaming tags cover part of the operational picture. Still missing for a streaming, credit-consuming tool: how long the stream runs, how it ends, and when to choose it over the eclipse webhook or totals siblings.

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?

Both optional parameters (fields, precision) are fully documented in the schema at 100% coverage, including example paths and rounding semantics, so the schema carries the burden. The description adds nothing about the compact-mode convention, so baseline 3 applies.

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 resource and output ('Countdown to next 5 eclipses'), which is concrete enough for an agent to know what it returns. It does not, however, distinguish itself from nearby siblings like astroway_stream_eclipse_totality or astroway_webhooks_eclipse_alert, so the boundary between eclipse-related tools is left to inference.

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 gives no when-to-use, when-not-to-use, or alternative guidance. An agent cannot tell from the text whether this should be preferred over the eclipse webhook or eclipse_totality tools, or under what conditions the streaming variant is appropriate.

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