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

Annotations already declare idempotentHint=true and destructiveHint=false, and the description reinforces this concretely: 'Every review already recorded stays, and ending a session again changes nothing.' That adds specificity about persistence and repeat-call behavior beyond the bare hint, though it largely restates what the annotations imply.

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 sentences, front-loaded with the usage condition followed by effects and the recap instruction; nothing is wasted. It is slightly longer than the tool's simplicity demands, and the idempotency sentence partly overlaps the annotations.

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 an output schema present, the return values need not be detailed, and the description still names them briefly. Usage condition, side effects, and idempotency behavior are all covered for a one-parameter session-ending tool with full annotation coverage.

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 single session_id parameter is documented as the value start_study_session returned. The description adds no parameter meaning beyond the schema, so the baseline of 3 applies for a fully documented single-parameter schema.

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 ('Closes the session') and its scope, plus what it returns ('its summary (cards reviewed, counts by rating)'). An agent can distinguish it from siblings like start_study_session, submit_review, and panel_grade without opening a 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?

'Use this when the user wants to stop studying before the cards run out, or after the last card' gives an explicit triggering condition covering both natural end states. No alternative tool is named for comparison, and no when-not case is given, 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.