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

Beyond the annotations, the description discloses that the tool writes *_r.xisf and .xdrz drizzle files, and that it is asynchronous, shows per-frame progress, and is cancellable. These are meaningful operational behaviors not captured in the structured annotations. No contradiction exists with readOnlyHint, openWorldHint, or destructiveHint.

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 three concise sentences: purpose first, output artifacts second, and operational behavior third. No filler or redundancy, and the structure is easy to scan.

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?

With six parameters, no output schema, and low schema coverage, the description leaves important details vague, such as parameter options, expected return value, and behavior of interpolation/distortion correction. It mentions output files but not enough for an agent to make correct parameter choices.

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%, covering just files and generate_drizzle. The description adds only the default reference source and mentions drizzle data output, but leaves out_dir, reference, interpolation, and distortion_correction completely unexplained. It fails to compensate for the low schema coverage.

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 identifies a specific operation: StarAlignment of frames to a reference, and names the default reference from select_subframes. It also states output artifacts, distinguishing it from integration or calibration tools. It does not explicitly differentiate from an 'align' sibling, but the phrasing is clear enough for an agent to infer the purpose.

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?

It provides context by referencing select_subframes as the default reference source, implying a typical pipeline position after frame selection. However, it does not explicitly state when to use this tool vs alternatives or give exclusion criteria, leaving the guidance partial.

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