Show a message on the mascot

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

Annotations already indicate it's not read-only (readOnlyHint=false), not open-world (openWorldHint=false), and not destructive (destructiveHint=false). The description adds behavioral context by stating the message is text-only and length-constrained, which is useful. However, it does not disclose whether the message persists, is transient, or has any side effects beyond the immediate display. Given annotations, the description meets the baseline but could add more context.

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 long, with the core purpose and key constraint front-loaded. It avoids redundancy and every word adds value. The sentence structure is direct and scannable, making it easy for an agent to quickly grasp the tool's function.

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 display tool with 3 parameters (one required) and full schema coverage, the description provides essential information: what it does, its limitations, and its scope. It doesn't explain return values, but the presence of an output schema suggests that is handled elsewhere. The only notable omission is explicit routing to sibling tools, but the 'text only' constraint implicitly covers that. Overall, it is sufficiently complete for its complexity.

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 100%, so all three parameters are documented. The description reinforces the text length limit ('up to 140 characters') which mirrors the schema's '140 Unicode scalars', and adds the constraint that only text is allowed. This adds marginal value beyond the schema but does not introduce new parameter-specific details that are absent from 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 clearly states the action (display), the resource (AI Coach mascot's speech bubble), and the constraints (short text, up to 140 characters, text only). It distinctly differentiates from `show_ai_coach_file` by explicitly ruling out images and links, so an agent can select the correct tool without ambiguity.

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 implies a usage context: use this for text-only messages. The phrase 'Text only; no images or links' signals that for other content types, a different tool (like `show_ai_coach_file`) should be used. However, it doesn't explicitly name the alternative or state when not to use it, so it's clear but not fully explicit.

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