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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the description's job is to add context. It does: groups are the targeting unit for campaigns (campaign.leadGroupName), and tags filter counts rather than groups. It does not mention pagination, result limits, or how many groups are typically returned.

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 short sentences, front-loaded with the action and return content, then the domain relationship, then the routing hint. Nothing is repeated and no sentence could be dropped without losing information.

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 3-parameter read tool with full annotation coverage and no output schema, this is nearly complete: it describes the returned data, the filter behavior, and the drill-down path. The only gap is any mention of the compact/full mode tradeoff, which is left entirely to the schema.

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 only 33%, but the description compensates for the hardest parameter: tags means OR semantics and filters the lead counts, not the group list itself. agentId is self-evident from the tool name, and mode is documented in the schema, though the description never mentions mode at all.

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 ("List the lead groups of an agent") and even names what the result contains ("the number of leads in each"). It also distinguishes itself from the sibling leads_read, so an agent can route between them without opening either 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?

Explicitly points to leads_read with groupName for the drill-down case, and explains the effect of the optional tags filter. It gives clear context but no explicit statement of when this tool should be preferred over other read tools (e.g. campaigns_read or contact_leads).

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