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

Annotations declare readOnlyHint=true, so safety is covered, but the description adds real value beyond that: the exact return shape ({nextShift:{userId, startTimeInUTC, endTimeInUTC}} or {}), the empty-result behavior, and the backing endpoint. It does not mention auth or pagination, but for a simple read that is minor.

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?

A single dense sentence front-loads the purpose, then the return shape, then the endpoint. Nothing is wasted, though the raw endpoint interpolation adds little for an agent selecting the tool.

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 output schema, the description usefully supplies the return shape and the empty-result case, which an agent needs. Combined with the readOnly annotation and full schema coverage, the definition is nearly complete; only explicit sibling routing is absent.

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 description coverage is 100%, so both parameters are already documented in-schema; the description only restates oncallId via the endpoint path and echoes the team-scoping. Baseline 3 is appropriate since the schema does the heavy lifting.

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+resource with a distinctive scope qualifier: 'Get the NEXT scheduled shift for an on-call schedule'. The 'NEXT' semantics cleanly separate it from sibling list/get tools like spike_list_on_calls and spike_get_on_call, so an agent can pick it without opening schemas.

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?

Usage is implied by 'NEXT scheduled shift' versus listing/current-shift siblings, but there is no explicit when-to-use, when-not-to-use, or named alternative. The '(team-scoped)' hint gestures at context without stating prerequisites.

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