What's changing — patterns ranked by delta vs baseline

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

Annotations already declare readOnly/idempotent/openWorld, so the safety profile is covered. The description adds genuine behavioral detail beyond that: the `min_delta_*` gates that drop noise-level changes, that `auto` averages three offsets, that brand-new patterns are EXCLUDED and routed elsewhere. It doesn't discuss rate limits or result size, but for a read-only analytical tool this is strong disclosure.

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 core purpose, exclusions, and usage examples are front-loaded and well organized. However, the sentence about restoring a deleted tool via commit 27dce7d and internal files (`top-volume-extras.ts`, `lib/gates.ts`) is implementation/commit archaeology that adds noise rather than helping an agent select or invoke the tool.

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 return-value explanation is unnecessary, and the description covers scope, gate behavior, exclusions, and use cases. It is complete enough to call correctly; the only minor gap is that the described return-row fields go a bit beyond what the output schema responsibility warrants, but nothing essential is missing.

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%, so the schema already documents all ten parameters, including the `comparison_window` offset semantics that the description largely repeats. The description reinforces the `timeRange`/`comparison_window` interaction with examples, but adds little that isn't already in the schema, making the baseline of 3 appropriate.

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+resource and the ranking axis: 'Patterns ranked by delta vs a baseline window.' It explicitly distinguishes itself from sibling `log10x_top_patterns` (which ranks by current cost) and from `log10x_whats_new` (brand-new patterns). An agent can identify exactly what this tool produces without opening 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?

Gives explicit when-to-use triggers ('what grew most this week', 'which patterns regressed after the deploy', 'what's driving cost up since yesterday') and names the alternative tools and conditions that select them (`top_patterns` for current cost, `whats_new` for new patterns, `pattern_trend`/`investigate` for sub-day spikes). Nothing is left to inference.

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