info

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

With no annotations, the description carries the full burden and does so well. It declares 'Read-only' upfront and explicitly states 'Never writes to or modifies the source file,' plus it enumerates the exact output fields. This fully discloses behavioral expectations.

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 with zero filler. The purpose is front-loaded ('Read-only metadata inspector'), followed by the output list and usage guidance. Every word earns its place.

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 simple metadata lookup with one parameter and no output schema, the description fully covers what the tool returns, when to use it, and that it is non-destructive. Nothing an agent needs to call it correctly 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?

The single parameter 'path' is fully described in the schema (100% coverage). The description adds no extra semantics beyond the schema's note about absolute or relative path, so it meets the baseline but doesn't exceed it.

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 clearly states it is a read-only metadata inspector and lists the specific fields returned (absolute path, format, width, height, color mode, file size). It differentiates from sibling manipulation tools by being informational, not transformative.

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?

It explicitly says 'Use it first to learn an image's dimensions or mode before resizing, cropping, or converting,' giving clear context for when to call it ahead of other operations. It doesn't enumerate alternatives, but the implication is strong enough for an agent to select it correctly.

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