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

The description explicitly discloses read-only behavior ('Read-only, never modifies the file') and rate/size limits ('Free tier: unlimited, any size'), which goes beyond the all-false annotations. Since the annotations do not make a positive claim, there is no contradiction.

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 focused sentences: the first front-loads the purpose and return fields, the second covers constraints. Every sentence earns its place with no 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 single-parameter inspection tool with no output schema, the description fully covers what the agent needs: the input, all returned data fields, read-only safety, and usage limits. Error cases are not described, but the low complexity makes this sufficient.

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?

The input schema already fully documents the single parameter ('path') with high coverage, so the description adds no additional parameter-level meaning. Baseline 3 applies because the schema carries the explanatory burden.

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 states a specific verb ('inspect'), a specific resource ('an image'), and enumerates the exact information returned (format, pixel dimensions, megapixels, file size, alpha channel). This distinguishes it clearly from sibling tools like image_dominant_colors or image_files.

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?

'Call this tool to inspect an image' provides an explicit when-to-use context, and the free-tier note adds practical guidance for using it as a lightweight inspection step. It does not explicitly name alternatives or when-not conditions, but the context is clear.

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