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

Annotations only declare the generic profile (readOnly=false, idempotent=false, destructive=false); the description supplies the real behavioral facts: a per-IP quota of 3 keys per 30 days, and a soft-failure mode where a key is still issued at $0 past the limit with the response disclosing it. That is quota policy and failure semantics an agent cannot get from annotations or schema.

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?

The creation action and credit grant are front-loaded, followed by the routing rules that matter most. The final email sentence is largely redundant with the schema and could be cut, but nothing else is padding.

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 creation tool with no output schema, it covers quota, failure behavior, and downstream tool requirements thoroughly. It stops short of saying that the issued key itself is returned in the response, which is the one fact an agent still has to infer.

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 100%, so both parameters are already documented. The description restates the email semantics (optional, used for delivery and top-up notices) almost verbatim from the schema and adds nothing about agent_name, so it earns only the baseline.

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 ("Creates an API key for this agent") plus the immediate consequence (grants free starter credits). It is unmistakably distinct from every sibling, none of which create credentials.

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 enumerates which tools require the key (purchase_data, check_balance, topup_credits, anything that charges credits), the special case for get_network_signals (paid tier + engines capability), and the negative case (every other read-only tool works without one). This is exactly the when/when-not/alternatives pattern.

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