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

Annotations already declare the safe read-only, idempotent, non-destructive, closed-world profile, so the description only needs to add context. It does: it discloses the per-item return fields (schedule, enabled state, next/last fire time) and the authorization scope (only accessible projects). Pagination or result-count behavior is not mentioned.

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 sentences, no filler, with the scope and returned fields front-loaded before the parameter usage note. Every clause carries information an agent needs.

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 compensates by enumerating the notable returned fields, and it defines global vs project-scoped behavior for a tool with one optional parameter. It stops short of mentioning pagination, ordering, or volume limits, which is the only remaining gap.

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 single parameter is fully documented in the schema, so the baseline is 3. The description earns above baseline by spelling out the behavioral difference between supplying projectId and omitting it (all accessible projects vs one project), which the schema's parameter text does not state.

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?

Names a specific verb (list) and resource (recurring agent missions / scheduled tasks) plus the scope (caller's accessible projects), and pre-empts the mission-vs-scheduled-task terminology overlap that exists among siblings like list_missions and list_scheduled_task_runs.

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 closing sentence gives a clear conditional: omit projectId to span all accessible projects, pass it to narrow to one. That covers the practical when-to-use decision, but it names no alternative tools and states no exclusions, so it falls 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.