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

Annotations already declare readOnlyHint/destructiveHint false, and the description adds real context beyond them: the hook-based delivery fallback, and a return shape ('summary lines, changed modules with exact signatures, anchored notes and live agents') that matters because there is no output schema. It doesn't cover latency, size limits, or failure modes, but it meaningfully exceeds the annotation baseline.

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?

The imperative 'Start here for any coding task' is front-loaded and the rest is dense, non-redundant information. It is a long single paragraph, but nearly every clause carries distinct content (contents, hook fallback, path behavior, read-only, return shape) rather than filler.

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 no output schema, the description does the work of describing returns, and it covers trigger, fallback semantics, and the optional blast-radius path behavior. What's missing is minor: guidance on choosing days/depth and any note on cost of a wide or deep query.

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, but the description adds the causal link that path/symbol 'also' trigger blast-radius computation rather than just filtering, which the schema does not convey. Depth's role is left to the schema, but the path/symbol behavior is genuine added meaning.

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?

It states a specific verb (get/generate a briefing) plus the exact resource content: 'the recent history of this repo — who changed what, renames to adapt to, hotspots, abandoned work and who is working right now.' The 'Start here for any coding task' opener and the enumerated contents distinguish it cleanly from siblings like recap, recall, and blast_radius.

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 clear trigger ('Start here for any coding task') and an explicit condition for calling it versus relying on ambient context ('Where Collide's hooks are installed the same briefing already arrives in your context; call this when it did not'). It also implies the blast_radius alternative ('Pass path ... to also get the blast radius') but never names that sibling explicitly, so routing is inferential rather than spelled out.

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