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. It discloses the behavioral trait of 'bypass permissions mode', which is valuable context not in the schema. However, it doesn't cover other important aspects like rate limits, error handling, or what 'trigger it to work' entails (e.g., does it return a response?). This leaves 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 a single, efficient sentence that front-loads the core purpose ('Send a message... to trigger it to work') and adds a key behavioral detail ('with bypass permissions mode'). There's no wasted text, but it could be slightly more structured by separating usage context from technical details.

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 no annotations and no output schema, the description is moderately complete. It covers the basic action and a permission detail, but for a mutation tool with 3 parameters, it lacks information on return values, error cases, or dependencies (e.g., session must exist). This leaves the agent with gaps in understanding full behavior.

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 parameters like session_id and message. The description adds no additional meaning beyond the schema, such as explaining message format or session_id sourcing. With high schema coverage, the baseline is 3, as the description doesn't compensate but doesn't need to heavily.

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 ('send a message') and target ('to a Happy AI session'), with the specific purpose 'to trigger it to work'. It distinguishes from siblings like happy_read_messages (read vs. send) and happy_start_session (start vs. interact). However, it doesn't explicitly differentiate from all siblings, such as those in the 'zen' family, which handle todos rather than session messages.

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 usage by stating the tool sends a message to trigger work, suggesting it's for interacting with an active session. However, it lacks explicit guidance on when to use this vs. alternatives like happy_start_session (for new sessions) or happy_read_messages (for retrieving messages). No exclusions or prerequisites are mentioned, such as requiring an existing session.

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