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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds genuine behavior beyond that: a null representation signals the source cannot be pinned, the response omits internal storage paths, and it returns frameCount and an exact fps ratio. That tells the agent what to expect on failure and what data comes back, which annotations alone would not.

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?

Three tight sentences, front-loaded with the action and precondition, followed by output semantics and a guardrail. Dense jargon ('certified decode representation', 'pinned') costs a point but nothing is wasted or redundant.

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 two-parameter read with no output schema, the description covers purpose, precondition, failure signal, and what the response surfaces (frameCount, fps). Only the provenance of the identifiers and how this differs from the inspect_* siblings are missing.

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 0% for both required parameters, so the description must carry the load. It names projectId and mediaId and implies mediaId must belong to the given project, but does not say where those identifiers come from (e.g., list_media/list_projects) or what form they take; the guidance is only partially compensating.

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?

A specific verb ('Read') and resource ('certified decode representation for media selected in this project') make the intent clear, and the phrase 'before starting an editorial run' anchors it to the editorial workflow. It does not differentiate itself from close siblings such as editorial_inspect_source or editorial_inspect_audio, which an agent could easily confuse with this tool.

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 first sentence gives a clear timing precondition ('before starting an editorial run'), and 'do not invent a source identity' is an explicit negative instruction telling the agent to derive values rather than guess. There are no named alternatives or exclusions, so a 4 is the correct ceiling.

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