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

Annotations indicate readOnlyHint=false, so the description doesn't need to justify the write nature. The description adds valuable context beyond annotations: the ping is visible to all clients (broadcast behavior) and stresses that x/y are scene-pixel coordinates, not grid squares. This clarifies important behavioral expectations that annotations do not cover. No contradiction with annotations.

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 three concise sentences with zero filler. The core purpose is front-loaded, then usage context, then a crucial parameter requirement. Each sentence earns its place, and the structure is easily scannable.

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 is adequate for a tool with 5 parameters (2 required) and no output schema. All parameters are documented in the schema, and the description adds the coordinate-system clarification and the broadcast visibility. It does not explain default values for style/duration, but those are derivable from the schema descriptions. The absence of output schema means no need to describe return values. Overall, an agent has enough to call it correctly.

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 baseline is 3. The description adds crucial clarification that x and y are REQUIRED and are in scene pixels (not grid squares), which directly impacts how an agent constructs valid calls. It also reiterates the purpose of these parameters. This added value justifies a 4 rather than a baseline 3.

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 ('drop'), a specific resource ('ping marker'), and the coordinate system (scene-pixel). It also names the effect ('visible to all clients') and the intended use ('draw players' attention to a spot'), clearly distinguishing it from sibling tools like canvas-pan (which moves the view) and ui-notify (which sends notifications).

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 states when to use this tool ('Use to draw players' attention to a spot'), giving clear context. It does not explicitly name alternatives or exclude other tools, but the purpose is specific enough that an agent could infer the appropriate scenario. The absence of an explicit 'instead of X' is a minor gap.

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