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

With annotations only covering safety flags, the description carries and delivers the real behavioral burden: the agent must supply repository data because 'Brainz can't read the repo', `complete` mutates last_synced_at and appends (never overwrites) to a concept, `complete` is rejected when coverage gaps are too large, and after ~14 days without a sync get_context and search results gain a staleness note — a cross-tool side effect not visible in annotations.

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?

Purpose is front-loaded and each sentence maps to a distinct action or consequence, with no filler. It is dense and slightly redundant with the schema's own parameter text (the append behavior and coverage rejection are stated twice), which keeps it short of a 5.

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?

There is no output schema, yet the description tells the agent what each action returns: `start` yields a drift playbook with last_synced_at, a coverage map and a re-index method; `status` yields onboarded state, staleness and counts. Combined with the mutation side effects and the ~14-day staleness consequence, an agent can call this correctly without further context.

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% and the schema descriptions already state the git-walk provenance, the append-not-overwrite behavior, and the rejection rule, so the description largely repeats structured data. It does tie the parameters to the workflow ('you run git ... and pass back changedPaths + areaList'), which adds modest value, but the baseline of 3 applies when the schema does the heavy lifting.

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 opening sentence gives a specific verb and resource — 'Re-index an onboarded vault after the code changes (drift)' — and the three action modes (start/status/complete) are each spelled out. The prerequisite ('an onboarded vault') implicitly separates it from the `onboard` sibling, though it never names `onboard` explicitly as the alternative for a first pass; that contrast only appears in the 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?

Each action has a stated purpose and the description explains the operating sequence: run git yourself, pass back changedPaths + areaList, then call complete to stamp the sync. It doesn't explicitly say when NOT to use it (e.g., for a vault that was never onboarded, or how it relates to `onboard`), so guidance is clear but not exhaustive.

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