Explain a diagnosis

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral content beyond that — the return surface (claim, resolved events, timeline, competing explanations, missing evidence, confidence breakdown) and the constraint against fabricating reasoning. It doesn't address latency or cost, but for a read-only explainer this is solid.

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?

Front-loaded with the core purpose ('Why diagnose_runtime reached its conclusion'), followed by a dense but purposeful enumeration of returned content and one usage sentence. The list is long but every element earns its place given there is no output schema; no filler.

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?

There is no output schema, so the description must carry the return-value burden, and it does so thoroughly by enumerating the claim, resolved evidence, timeline, competing explanations, gaps, and confidence breakdown. Combined with zero parameters and clear annotations, nothing an agent needs to call it correctly is missing.

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?

The tool takes zero parameters, so per the rubric the baseline is 4. There is nothing for the description to disambiguate at the parameter level.

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 names a specific verb (explain) and resource (the diagnosis produced by diagnose_runtime), and it explicitly frames the tool as the 'why' counterpart to diagnose_runtime. An agent can distinguish it from siblings like diagnose_runtime or get_timeline without opening any schema.

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?

It gives a clear triggering condition: 'Use to answer "why do you think that" without inventing reasoning,' which implies invocation after a diagnose_runtime conclusion. It doesn't explicitly name alternatives or exclusions, but the usage context is unambiguous.

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