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

Annotations already declare readOnlyHint, destructiveHint=false, and openWorldHint=false, so safety is covered. The description adds one genuinely new behavioral fact — the default sort order (most recently active first) — but says nothing about pagination behavior or total counts.

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?

One short sentence with no filler, and the resource is front-loaded ahead of the sort detail. Near-optimal density for what it says, though it could have used the same brevity to include a sibling pointer.

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 two-parameter read tool with full annotation coverage and full schema coverage, this is minimally adequate: ordering and scope are stated. It leaves out result shape (no output schema exists) and does not clarify how it relates to search_contacts or list_leads, which an agent needs to route correctly.

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 both the limit (default 25, ceiling 100) and the lifecycle_stage enum are fully documented in the schema. The description adds no parameter detail beyond what the schema already carries, so baseline 3 applies.

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 contacts') plus scope ('for this account'), which is more than a restatement of the title. It does not distinguish itself from the sibling search_contacts, so an agent still has to guess which enumeration tool to pick.

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 'for this account' scoping and 'most recently active first' ordering imply a browse/list use case rather than a filtered lookup, but no alternative is named and no when-not-to-use guidance is given. Usage must be inferred from the sibling list rather than from the text.

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