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

With no annotations, the description carries the full burden. It discloses that the tool returns a full chain with timestamps and implies a read-only trace operation. It doesn't cover edge cases, but for a GET-like tool this is adequate.

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?

Four concise, front-loaded sentences. Each sentence earns its place: purpose, trigger, return value, and usage rule. No filler or redundancy.

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 tool with an output schema, the description covers purpose, usage, and return well. However, the undocumented decision_id and the misleading example leave a real gap in correct invocation, making it only minimally viable.

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 0% and the description never defines the decision_id parameter. The example ('Rachel moved to Chicago') refers to a value, not a decision_id, which could mislead the agent into passing the wrong kind of input.

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 uses a specific verb ('Trace') and names the resource ('how a fact or decision evolved over time'). It explicitly states the return type ('full version chain with timestamps') and distinguishes itself from siblings like get_causal_chain by focusing on supersession across sessions.

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?

Provides explicit when-to-use guidance: call it when you find a value that might be superseded, and ALWAYS for 'current', 'now', or 'most recent' questions. It does not mention when not to use it or name alternatives, so it stops short of a 5.

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