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

Annotations already establish readOnlyHint=true, destructiveHint=false and openWorldHint=false. The description adds genuinely new context beyond them: the file itself is never sent, so the agent knows this is a pure local computation over supplied values rather than an upload or inspection.

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 tight sentences, zero filler, with the core capability front-loaded and the usage condition immediately after.

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?

There is no output schema, so the description carries the burden of describing the return value, yet it never says what a check produces (pass/fail, which rule was violated, how the free-form rules_text is matched). The usage hint partially compensates, but the result contract is 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 coverage is 60% (only format, rules_text and file_size_bytes are documented). The description usefully maps its three concepts onto parameters ('size in bytes', 'pixels', 'type') and hints where the values come from, but adds no syntax, ranges, unit or enum detail beyond that mapping.

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 (check) and resource (file size in bytes, pixels, type) against website upload rules, and clarifies it does so without sending the file. It does not name a sibling such as interpret_upload_rules, so differentiation is implied rather than explicit.

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 a clear triggering condition: 'Use when you already know the numbers (e.g. from the file's properties).' It does not name the alternative tools to use when the numbers are unknown, nor state any exclusions.

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