Check a file for AI marking

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

Annotations already declare readOnlyHint=true and openWorldHint=true, and the description adds genuinely new context: the call consumes API quota ('Counts as one API call') and the result includes both signature validity and a match against the account's records. It doesn't cover limits like per-account quotas or failure modes for unmarked files, but what it adds is substantive.

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 sentences, front-loaded with what is inspected, followed by when to use it, then the cost note. Nothing is redundant and no sentence 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 does the right thing by naming the reported fields (signature validity, record match). Read-only and open-world behavior are covered by annotations. It is slightly thin on what an unmarked or unmatched file returns versus an error, but it is largely complete for a two-parameter check tool.

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% and both parameters are documented with size limits and the 4.5 MB vs 25 MB URL/path split. The description only restates 'image or audio file' and adds no format, precedence, or mutual-exclusivity guidance (e.g. what happens if both url and path are supplied). Baseline 3 applies where the schema carries the weight.

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 ('Checks an image or audio file') and enumerates exactly what it inspects: Markproof watermark, C2PA manifest, signature validity, and account record match. That scope is inherently distinct from the sibling mark_file (which writes a mark) and get_asset, so an agent can pick correctly without opening either schema.

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 two concrete usage conditions: confirming a file is marked before publishing, and inspecting a file of unknown origin. It stops short of naming mark_file as the alternative for the 'file is not yet marked' case, so the routing is clear but not fully explicit.

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