Happy Server MCP

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

With no annotations provided, the description carries full burden but offers minimal behavioral insight. It mentions the toggle behavior when 'done' is not provided, which is useful, but lacks critical details: whether this requires specific permissions, if changes are reversible, what happens on success/failure, or any rate limits. For a mutation tool with zero annotation coverage, this leaves significant gaps in understanding its operational behavior.

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 a single, efficient sentence that front-loads the core action ('set or toggle') and resource. Every word earns its place by clarifying the tool's function without redundancy or fluff. It's appropriately sized for a simple tool with two parameters.

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?

Given this is a mutation tool with no annotations and no output schema, the description is insufficiently complete. It doesn't cover error conditions, response format, or side effects, leaving the agent to guess about outcomes. While the purpose is clear, the lack of behavioral and output context makes it inadequate for safe and informed use.

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 fully documents both parameters ('id' and 'done'). The description adds marginal value by explaining the toggle behavior when 'done' is omitted, but doesn't provide additional context like ID format examples or edge cases. This meets the baseline for high schema coverage without enhancing parameter understanding significantly.

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 verb ('set or toggle') and resource ('a Zen (todo) item completion status'), making the purpose immediately understandable. It distinguishes from siblings like 'happy_zen_create_todo' or 'happy_zen_update_todo' by focusing specifically on completion status manipulation. However, it doesn't explicitly mention that this is for existing todos only, which would make it a perfect 5.

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 provides no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., needing an existing todo), compare with 'happy_zen_update_todo' which might also handle status changes, or specify scenarios where toggling versus explicit setting is preferred. The agent must infer usage from the tool name and parameters alone.

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