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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description still adds value by disclosing the shape of the returned data (name, type, duration, size, folder, encoding state) and noting that metadata is opt-in, which matters because there is no output schema.

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?

Two sentences, zero filler, with the core purpose front-loaded and the conditional metadata guidance placed in the second sentence. Nothing here could be dropped without losing information.

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 no output schema, the description compensates by listing the returned fields, and it explains the optional metadata expansion. Minor gaps remain around error behavior for an invalid or missing id, but the essentials for calling it correctly are present.

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 100%, so both fileId and includeMetadata are already well documented, including the id pattern and the default of false. The description's mention of resolution, frame rate and codecs largely restates the schema text, so it adds little beyond the baseline.

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 resource ('Read one file from the media library by id') and enumerates the returned fields, which cleanly separates it from the list-oriented sibling livereacting_list_media. An agent can tell instantly that this is the single-item fetcher.

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 concrete guidance for the includeMetadata flag ('when you need the technical detail') and ties it to a downstream decision (whether livereacting_encode_media is required). It does not state when to prefer this tool over alternatives, but the encode_media workflow context is genuinely useful.

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