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

Annotations already convey read-only, idempotent, and non-destructive behavior. The description adds meaningful context beyond annotations: no API key required, free preview, and a rate limit of 20 queries/session. It also notes the listing price, giving the agent a realistic sense of cost expectations for the underlying data service.

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 description is a promotional run-on block with clear redundancies: 'No API key needed' is repeated in the last sentence, and 'FREE preview' is stated twice. While the key call-to-action is front-loaded, the final 'Try one of the sample questions now' is filler that does not earn its place.

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 simple tool with two optional parameters and no output schema, the description covers the essentials: free, no auth, listing identity, and typical sample questions. However, the fact that the preview returns 'public metadata only' is hidden in the input schema description rather than the main description, leaving slight ambiguity about what the agent will actually receive.

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 parameters are already fully documented in the input schema with 100% coverage, so the schema carries the meaning. The description adds sample questions that illustrate how the question parameter might be used, but it does not clarify parameter syntax, formatting, or edge cases beyond what the schema provides.

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 clearly identifies a free preview of the spaceweather listing and invites sample questions, establishing a specific action (preview) and resource. The tool name and annotation title 'Preview Data Listing (Free)' reinforce this. It does not explicitly define the output (public metadata only appears in the schema), but the overall purpose is unmistakable.

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 says 'No API key needed — call this now' and provides sample questions, implying immediate use without setup or prerequisites. However, it never explicitly states when to prefer this tool over siblings like data_session_query or data_session_open, so usage guidance remains implicit rather than prescriptive.

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