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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the mutation risk is known. The description adds valuable behavioral context: reusing a path doesn't consume another image slot, new paths are subject to allowance, Carryo imports and hosts its own copy, and base64/data URLs are unsupported. This goes beyond the annotations without contradicting them.

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?

The description is dense but well-structured, front-loading the core action and then explaining key constraints. Every sentence adds information. It's slightly long but justified given the complexity of the tool's behavior (allowance, path reuse, source types).

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?

The description covers the essential behavioral rules: path reuse, allowance, source requirements, and unsupported formats. The output schema exists, so return values don't need explanation. Minor gaps: it doesn't explicitly state what happens when removeAssetPaths conflicts with assets, or whether the operation is atomic, but these are edge cases.

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 the schema already documents all parameters thoroughly. The description adds meaningful context beyond the schema: the distinction between reusing a path (no extra slot) vs new paths (allowance applies), and the import/hosting behavior. This is above the baseline 3 because it clarifies the semantics of the assets array and the relationship between fileId and sourceUrl.

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 ('Adds, replaces, or removes') and resource ('hosted images on an existing Carryo website'), and explicitly distinguishes itself from website.edit by noting it does not replace HTML. This clearly differentiates it from sibling tools like website.edit and website.save_draft.

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?

The description explains when to use this tool (to manage images without touching HTML) and provides clear context about path reuse, image allowance, and source requirements. It doesn't explicitly name alternatives or say 'use X instead', but the context is strong enough for an agent to select it appropriately among siblings.

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