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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds non-obvious semantics that structured fields cannot: an unmeasured axis is a first-class published answer, never an error and never a zero, and the output is never a certification. That is real behavioral context an agent would otherwise mis-handle.

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 identity and URL, then the field list, then the unmeasured rule. Dense but every clause earns its place except the mild redundancy of listing return fields when an output schema already exists.

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?

Output schema exists, so return values needn't be described, yet the field list is harmless framing. Annotations cover safety. The one gap is the absence of routing guidance among the many sibling axis tools, which leaves selection partly on naming convention.

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, which is the baseline 4. The description explicitly confirms 'it takes no argument', removing any doubt an agent might have about needing to supply an axis id.

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?

Identifies itself precisely as the effect-binding axis of the live GSPC board and enumerates the fields a row carries (n, accuracy, interval, status, family, kind, URL, dates). Sibling axes follow the same naming pattern, so the title alone disambiguates; the description reinforces it but doesn't explain how this differs from get_axis or measurement_index.

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?

No statement of when to fetch this axis versus the sibling get_axis or measurement_index endpoints, and no prerequisites or exclusions. The only guidance is internal semantics of the unmeasured case, which is about interpreting the result, not choosing the tool.

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