Happy Server MCP

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It mentions optional Git worktree creation for isolated development, which adds useful context beyond the basic action. However, it lacks details on permissions, rate limits, session lifecycle, or error conditions, leaving gaps for a mutation tool.

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 appropriately sized with three sentences, each earning its place: the core purpose, prerequisite tools, and optional Git worktree feature. It is front-loaded with the main action. Minor improvement could be tighter phrasing, but it avoids waste.

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 the tool's complexity (8 parameters, mutation operation) and no annotations or output schema, the description is moderately complete. It covers purpose, prerequisites, and a key optional feature, but lacks details on behavioral traits like side effects, response format, or error handling, which are important for a session-starting tool.

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 8 parameters thoroughly. The description adds minimal parameter semantics beyond the schema, only implying that 'machine_id' and 'environment_preset_id' relate to outputs from sibling tools. Baseline 3 is appropriate as the schema does the heavy lifting.

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 specific action ('Start a new Happy AI session') on a specific resource ('on a machine'), distinguishing it from siblings like happy_list_sessions (list) or happy_send_message (interact). It explicitly mentions the verb 'start' and the resource 'session', avoiding tautology with the tool name.

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 explicit guidance on when to use this tool versus alternatives: it instructs to 'Use happy_list_machines to find available machines first' and 'Use happy_list_environment_sets to see available environment presets', naming specific sibling tools for prerequisite steps. This clearly defines the context and alternatives.

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