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

Annotations already cover read-only, idempotent, non-destructive, closed-world, and the description reinforces this by ruling out rerender/edit side effects. It adds that outputs are unaligned and that views/crop affect only diagnostic evidence, not the underlying composition. It does not cover failure modes (e.g., mismatched resolutions or stale identities), which keeps it below a 5.

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?

Five tight sentences with the core action and return shape front-loaded, followed by prerequisites and caveats. Dense terminology ('certified representation', 'explicit event correspondence') costs some readability but no sentence is filler.

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 nested-object comparison tool with an output schema (so return values needn't be spelled out), the description covers inputs' provenance, side-effect guarantees, and the retiming caveat. The main remaining gap is what the caller should do when comparison preconditions fail.

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?

With only 50% schema description coverage and nested objects, the description does real work: it tells the agent where reference.mediaItemId/representationIdentity and candidate.jobId/artifactId come from, and clarifies that views are optional and that crop uses identical coordinates across both frames. It still leaves the required/optional status of views and the crop bounds implicit.

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 verb and two specific resources (a certified reference frame vs. an existing full-resolution PNG preview) and names the exact output artifacts. It is clearly distinguishable from preview_frame (which produces the candidate) and editorial_run_source (which supplies the reference identity).

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?

Gives an explicit prerequisite chain: read editorial_run_source for the reference identity, then preview_frame + wait_job for the candidate artifact. It also states the exclusion ('never rerenders or edits the composition') and the retiming caveat that selects a different correspondence strategy.

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