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

Annotations already declare readOnlyHint=true, and the description adds useful behavior: grouping, direction semantics ('inbound = money in, outbound = money out'), aggregate fields, and 'Groups are ordered largest-first'. This goes well beyond the annotation without contradicting it.

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?

Three sentences deliver the core purpose, the output contents, the direction semantics, the ordering, and the intended follow-up action. Every sentence earns its place and the main function is front-loaded.

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 read-only summary tool with one optional parameter and an output schema, this description is complete. It tells the agent what the response contains, how it is ordered, and how to act on it, leaving no critical gap.

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% and the only parameter, org_id, is fully documented in the input schema. The tool description adds no extra parameter-level meaning, so the baseline 3 is 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 and resource: 'Summarises the review queue clustered by counterparty and direction'. It also explains the exact grain ('the exact grain a rule is keyed on'), which clearly distinguishes it from per-transaction review tools like get_unreviewed_events.

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?

Explicitly gives the usage pattern: read this summary to decide once per vendor, then call create_counterparty_rule to categorise a whole counterparty. It contrasts this with deciding 'per transaction', so an agent knows when this tool is the right choice.

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