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

Annotations already declare destructiveHint=true, idempotentHint=false, and openWorldHint=true, so the description's restatement of non-idempotency is confirmatory rather than additive. It does add real value by disclosing the downstream consequence — 'May unlock point-based rewards' — which explains why the operation is flagged destructive.

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?

A single compact line with the operation type front-loaded and zero filler. Every clause (mutation, idempotency, reward side effect, endpoint) carries 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?

With no output schema, the description should signal outcomes, and it does hint at reward unlocking. For a 7-parameter mutation, the description plus the rich schema and explicit annotations cover what an agent needs to call it safely, though it never clarifies which identifier field takes precedence.

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 the schema already documents every parameter, including the five mutually exclusive identifier fields. The description only adds the abstract notion that the subscriber is identified by the campaign's unique identifier, without mapping it to the specific identifier parameters; this is baseline-appropriate but no better.

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 ('add points to an existing subscriber') and front-loads 'WRITE:', making the mutation nature unmistakable. It also names the endpoint, which distinguishes it cleanly from siblings like referralhero_add_coupons or referralhero_update_subscriber.

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?

Gives clear context for when to invoke it (existing subscriber, campaign-scoped) and warns that repeated calls stack points. It does not explicitly rule out or compare against alternatives such as referralhero_add_coupons or referralhero_update_subscriber, so it stops short of full routing guidance.

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