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

Annotations already establish read-only, idempotent, non-destructive behaviour, so the bar is lower. The description still adds genuine context beyond them: the values are 'precomputed' and scoped to 'the current work-unit snapshot', signalling data freshness and isolation limits an agent would otherwise have to guess.

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 short sentences, no filler, with the core purpose front-loaded and the limitation carried in the second sentence. Every clause earns its place.

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 detail is unnecessary. The description covers what is returned, the snapshot scope, and the two things it does not do, which is enough for a low-complexity, zero-required-parameter read tool. Only the absent sibling routing keeps it from a 5.

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 explains 'category' and 'entity_name' fully, setting the baseline at 3. The description adds nothing about how these filters interact (e.g. whether entity_name is required, or how category narrows lines), so it neither helps nor harms.

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?

Names a specific verb and resource with real precision: 'reads precomputed revenue, units and margin per product', and scopes it to 'the current work-unit snapshot'. An agent knows exactly what data comes back. It does not explicitly differentiate itself from any sibling by name, which keeps it just below a 5.

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 second sentence supplies useful negative guidance ('no date series or whole-workspace totals'), which tells the agent this is not the tool for trends or aggregate rollups. However, no alternative tool is named for those cases and there is no positive 'use this when' framing, so the routing guidance remains 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.