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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, non-destructive, closed-world), so the bar is lower. The description still adds real behavioral context beyond them: cross-session reachability, output-field parity with fetch_leads, and the get_campaign_stats bucket-resolution use of leadIds.

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?

Front-loaded with purpose in the first clause, then differentiation against fetch_leads, then the leadIds workflow tip. Tightly written with little waste, though the 'same fields as fetch_leads, including score and scoreExplanation' clause is mildly verbose.

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?

A read-only, 3-parameter tool with a full schema, an output schema, and complete annotations is well-covered by this description. The cross-session caveat and sibling differentiation are the key additions; nothing critical for correct invocation 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 baseline is 3. The description goes slightly beyond the schema by explaining what leadIds accomplishes in workflow terms ('resolves the reply buckets from get_campaign_stats back into named people'), adding use-case meaning beyond the schema's raw field documentation.

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 ('Returns the leads of any campaign by campaignId') and immediately distinguishes itself from the sibling fetch_leads by scope. An agent can tell what it does and how it differs from fetch_leads 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?

The description explicitly states the selecting condition: it 'covers campaigns not started in this session, which fetch_leads cannot reach,' and explains why (fetch_leads requires a same-session jobId). This effectively routes the agent to the right tool, though it does not state explicit when-not conditions or mention the other siblings.

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