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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds that results are per-schedule rather than a single flat answer, which tells the agent to expect multiple entries. It does not cover the empty case (nobody on call) or whether schedules with no rotation are omitted, which is the one remaining behavioral gap.

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?

Two short sentences: the first states what is returned, the second states when to call. No filler and nothing buried.

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?

With no parameters and no output schema, the description carries the return-shape burden and does it: person plus shift-end timestamp per schedule. Missing only the edge-case behavior (no one on call, multiple rotations), which keeps it from a 5.

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 there is nothing to disambiguate and the baseline applies. The description correctly frames the call as taking no input scope.

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 and resource ('Get the person currently on call for each on-call schedule') plus the returned datum ('when their shift ends'). This is clearly distinguishable from the incident-oriented siblings, none of which expose on-call ownership.

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?

Explicitly names the triggering situation: 'Call this when deciding who to contact about an incident.' That ties it to the incident workflow siblings nicely, but it doesn't state when not to use it or offer a contrasting alternative (e.g. escalation policies), 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.