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

Annotations only declare readOnlyHint=true; the description adds substantive behavioral context beyond that, disclosing the per-call cost ($0.02/call) and the shape of the returned reasoning. It does not mention rate limits or latency, but the cost disclosure is a meaningful operational trait an agent should know before invoking.

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 sentences, front-loaded with what the tool returns, then when to use it, then the id source and cost. No filler and every clause carries distinct 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?

No output schema exists, but the description enumerates the return content (rationale, graph path, source link, corroboration), so an agent knows what to expect. Combined with the read-only annotation and the id-provenance note, nothing needed 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?

Schema coverage is 0% and the single param has no schema description, but the description compensates by explaining provenance: 'Takes the event id from those tools' (events_since/impact_for). That tells the agent where a valid value comes from, which the bare string-typed event_id field does not.

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?

States a specific verb (explain) and resource (ONE event's impacts) and enumerates exactly what the explanation contains: direction/confidence rationale, exposure-graph path, source document link, corroborating sources. It also distinguishes itself from siblings events_since/impact_for by naming them as the source of the event id rather than duplicating their role.

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?

Gives explicit triggering conditions: use when an impact from events_since/impact_for is surprising and you need the reasoning before acting, or when you want to log a rationale. Both the alternative tools and the when-to-use condition are named, leaving little to inference.

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