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

Annotations already declare this is a non-read-only, non-destructive, idempotent, closed-world mutation, so the safety profile is covered. The description adds genuinely new behavior beyond that: the call returns an Undo, which tells the agent a rollback path exists after a successful move. It does not address conflict handling with existing sessions or whether past sessions can be moved, which keeps it from a 5.

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?

Three short sentences: trigger, required inputs, return behavior, then the exclusion. The trigger and the exclusion are front-loaded and prioritized, and no sentence is redundant.

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 4-required-param mutation with full annotation coverage and an output schema, the description covers purpose, inputs, exclusion, and the undo affordance, so return-value detail is correctly omitted. Only edge cases like scheduling conflicts or moving past sessions are unaddressed.

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 only 25% (just idempotencyKey documented), so the description has to compensate, and it does by naming sessionId and clarifying that start and end are 'the new' times supplied as ISO strings. That resolves the ambiguity of whether the times are the old or new values. It still doesn't say where sessionId comes from (e.g. get_schedule), leaving one 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 states a specific verb and resource ('move a session') plus the scope ('to another day or time'), and explicitly distinguishes itself from update_session. An agent can pick this over the sibling without inspecting either schema.

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?

It gives a positive trigger ('when the person asks to move a session to another day or time'), a negative case ('Do not use to skip a session'), and names the correct alternative ('use update_session'). Nothing is left to inference about when to pick this tool.

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