Explain why an event scored the way it did

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

With no annotations, the description carries the full burden. It discloses what the tool returns (event, checks, weights, raw evidence) and that it is 'Free', but it does not explicitly state whether it has side effects, requires certain permissions, or has other operational constraints. This leaves some ambiguity, though the read-only nature is strongly implied.

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 two short sentences plus 'Free.', front-loaded with the purpose ('why was this blocked?') and then a compact, informative explanation of the output (every check, weight, evidence). Every word earns its place; no fluff.

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 one-parameter tool with no output schema, the description does a good job conveying what the caller will get (event with checks, weights, evidence). It could be slightly more complete by mentioning whether the event itself is returned in full or just the analysis details, but the phrase 'Returns the event with...' sufficiently covers this.

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 schema already describes the only parameter (event_id) as 'The event id, as returned by list_events', achieving 100% schema description coverage. The tool description does not add any additional parameter-specific information beyond what the schema provides, so the baseline of 3 is appropriate.

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 tool's purpose: explaining why an event scored as it did, specifically by returning the event with all checks that fired, their weights, and raw evidence. This specific verb-resource pairing ('explain event') distinguishes it from siblings like score_event (which likely computes the score) and investigate_entity (which sounds broader).

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 phrase 'The ‘why was this blocked?’ tool' gives a clear situational context for when to use this tool. It implies you should use it when you need the reasoning behind a score/block decision rather than just the score itself. However, it does not explicitly mention when not to use it or name alternative tools, so it's not a full 5.

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