observe_tool_start

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

Discloses return value (callId), threading mechanism, and event emission (toolCall:start). With no annotations provided, description carries full burden and meets it well for a start-observation 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?

Three concise sentences, front-loaded with version and primary action. No superfluous information.

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?

Explains return value, threading pattern, and event emission. Lacks error handling or validation details for toolName, but adequate for a simple start tool with no output schema.

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 covers 50% of parameters with descriptions (only args has description). Description adds no extra meaning beyond what schema provides; toolName lacks any context or constraints. Does not compensate for schema gaps.

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?

Description clearly states the tool begins observing a tool call, returns a callId, and is part of a family (observe_tool_complete/error/partial/cancel). It distinguishes itself as the initiation point among sibling observation tools.

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?

Implied usage as the first step in a sequence of observation calls, but no explicit when-to-use or when-not-to-use guidance. No comparison with alternatives beyond listing sibling names.

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