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

Annotations already declare non-read-only, idempotent, non-destructive, but the description adds the behavior that matters: the entry is protected from History pruning and a doc is capped at 10 saved points. That retention limit is genuine context not derivable from structured fields. It doesn't say what happens when the cap of 10 is reached (error vs eviction), 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?

Two compact sentences, front-loaded with the action and its consequence, followed by the retention cap. The nested parentheses make it slightly dense on first read, but no sentence is wasted.

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 3-parameter tool with full schema coverage and no output schema, the description covers effect, defaults, the note parameter, and the retention limit – enough to call it correctly. Only the cap-reached behavior is left unspecified.

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 the baseline is 3. The description's default note essentially restates the schema's "Default: the current entry." The one addition is "a sheet: as it is now", clarifying that saving snapshots sheet state, but overall it adds little beyond the schema text.

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 verb+effect ("keeps ... as a saved point" so "History never drops it") is specific and identifiable, and it distinguishes itself from the sibling `history` by describing a pin/retention action. It stops short of naming a sibling alternative, but the action itself is unambiguous.

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 parenthetical explains the two practical cases – default to the current entry, or pin a sheet's present state – which implies when to call it. It never states when NOT to use it or how it relates to `history`, `restore`, or `changes`, so guidance is implied rather than explicit.

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