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

The description's opening verb is "Creates a ... focus session" with a running timer, while the annotations declare readOnlyHint=true — a start-session action does change application state, and the description does nothing to reconcile that. Beyond that mismatch, the description does add useful behavioral context (short blocks, movement breaks sized to energy), but it says nothing about what happens when parameters are omitted or what the tool returns.

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, front-loaded with the core action and followed by the differentiator and the use case. No filler, no repetition of the title, and every clause carries information.

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 and all parameters optional, the description should say what happens on a bare call (default duration/energy) and roughly what the agent gets back (session started? timer handle?). It covers the concept well but leaves the agent guessing about invocation defaults.

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 coverage is 100%, so all three parameters are already documented, but the description adds real meaning: it explains why energy_level exists (breaks are "sized to the user's energy") and what minutes produces (short focus blocks with movement breaks). It does not state defaults for the optional task/minutes/energy_level arguments, which is the remaining gap.

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 gives a concrete verb and resource ("Creates a pain-friendly focus session") plus the mechanism ("paced pomodoro ... live timer that grows a plant"), which is far more specific than the name alone. It implicitly separates itself from siblings like start_calm_exercise by framing the activity as timed focus blocks, but it never names or contrasts any alternative tool.

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?

"Use for focusing, studying or working with brain fog, chronic pain or fatigue" gives a clear positive trigger tied to user state, which is exactly the kind of context an agent needs for a wellness tool. It stops short of exclusions or routing rules (e.g., when to pick this over start_calm_exercise or plan_paced_day), so it is context without alternatives.

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