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

Annotations already declare readOnlyHint=false, idempotentHint=false, and destructiveHint=false, so the description doesn't need to restate those. The description adds useful behavioral context: the notification is transient by default, appears for every connected client, and 'permanent' keeps it on screen until dismissed. It also clarifies that 'type' controls colour/severity. 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 two sentences with zero waste. It front-loads the core purpose, then adds the key distinction from chat-send and the parameter semantics. Every sentence 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 notification tool with 3 parameters, full schema coverage, and no output schema, the description is complete enough. It covers the tool's scope, the key alternative, and the behavioral effect of the parameters. The only minor gap is that it doesn't mention whether the notification is visible to the GM only or all players, but 'every connected client' already implies broad visibility.

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 three parameters (message, type, permanent). The description adds a little extra meaning by explaining that 'type' controls colour/severity and that 'permanent' keeps it on screen until dismissed, but it doesn't add substantial new semantics beyond the schema. Baseline 3 is appropriate.

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 ('Show a toast notification'), a specific resource ('in the Foundry UI of every connected client (ui.notifications)'), and explicitly distinguishes itself from chat-send ('not a chat message'). This clearly differentiates it from sibling tools like chat-send and chat-update.

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 explicitly says when to use this tool ('Show a toast notification...') and when not to ('not a chat message (use chat-send for chat)'). It also explains the effect of the 'permanent' parameter, giving clear context for choosing this tool over alternatives.

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