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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds genuine value beyond that by scoping exactly what data comes back (lists, tags, custom fields, consent, lifetime value, subscribed/suppressed state), which is meaningful since no output schema exists.

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 tight sentences with no filler; the payload contents are front-loaded before the endpoint reference, so nothing has to be skimmed past.

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?

With no output schema, the description carries the burden of describing return contents and does so concretely. It is nearly complete for a single-record read; only error/not-found behavior is unaddressed, which is minor.

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 0% and the single contact_id parameter carries no description, but its name and integer type make it self-evident. The phrase 'by id' confirms identity lookup but adds no format, range or lookup-failure semantics beyond the schema.

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 (get) and resource (one contact) keyed by id, which clearly separates it from the sibling sendlane_list_contacts. It does not explicitly name the sibling it is the singular counterpart to, so it stops short of 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?

Usage is implied: the enumeration of lists, tags, custom fields, consent and subscription state suggests this single call can replace the narrower sendlane_get_contact_tags / sendlane_get_contact_subscriptions calls, but the description never says so outright and gives no when-not conditions.

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