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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds a genuine behavioral detail: only committed (not in-progress) selections are returned, and selection_task_id is present only for request_part_selection-derived selections. It says nothing about what happens with an invalid/closed session or an empty selection.

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 dense sentences with the core purpose front-loaded and no filler. The third sentence about realign is a useful cross-reference, though it slightly buries the primary contract.

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?

An output schema exists, so explaining return values is optional; the description nevertheless frames the key conditional field and the realign downstream use. For a single-param read tool with full annotations, this is nearly complete, missing only error/empty-selection behavior.

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?

One parameter at 0% schema coverage, so the description must carry meaning; it does imply the id must refer to an open map session, which is real semantic value. However it gives no format, source, or failure behavior for the id, so compensation is only partial.

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?

Specific verb+resource: it retrieves the most recent committed selection for an open map session, and enumerates the payload (part_layer, part_ids, selection_task_id). It scopes itself with 'selections the person started from the map legend', which helps separate it from the similarly named get_part_selection, but it never names that sibling explicitly.

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?

Usage is implied rather than stated: the agent learns this applies to map-legend-originated selections on an open session, and that realign consumes these part_ids. There is no explicit when-not-to-use or direct pointer to the alternative get_part_selection for other selection sources.

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