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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the safety profile is covered. The description's only behavioral addition is the local-date/format constraint and date-range scoping, both of which are largely mirrored in the schema; it does not describe return shape, ordering, or empty-range behavior.

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, front-loaded with the resource and scope, followed by the one non-obvious input constraint. No filler.

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 two-parameter read tool with full schema coverage and annotations declaring a safe read, this is nearly complete. The only gap is that without an output schema, nothing tells the agent what fields a returned session record contains.

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% and the schema already documents both start and end as local YYYY-MM-DD, including the 180-day max on end. The description reinforces the local-date convention but adds no new syntax or semantic detail, so baseline 3 applies.

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 ('List mindfulness sessions') plus the domain covered (meditation, breathing, relaxation). It is clear what the tool returns, but it does not explicitly differentiate itself from siblings like get_workouts or get_daily_summary, which an agent may also consider for activity data.

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 instruction to pass LOCAL dates in strict YYYY-MM-DD implies the usage context (querying a history window), but there is no guidance on when this tool is preferred over alternatives or what happens outside the date range. Usage is implied rather than stated.

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