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

Annotations already declare readOnlyHint=true and destructiveHint=false, covering the safety profile. The description adds the append-only ledger nature and event types, which is useful, but does not disclose pagination, ordering, or response format. This is some added value but not rich behavioral context.

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 description is a single, dense sentence that front-loads the core scope ('Append-only Ledger events for this caller_id'). It is efficient and contains no wasted words, but the heavy use of jargon ('first_key', 'reason=inbox_mint') makes it less approachable for an agent.

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 simple no-parameter read-only tool, the description covers the event categories and endpoint, which is adequate. However, without an output schema, missing details about response format, pagination, or ordering could leave an agent uncertain about what to expect. The description is sufficient but not fully complete.

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?

The tool has zero parameters and the schema is effectively complete. The description's mention of event types is extra informational context, not parameter semantics. With 0 parameters, the baseline is 4, and the description does not need to compensate.

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?

The description clearly identifies the resource (credit ledger events) and the endpoint (GET /credits/events), enumerating specific event types. It distinguishes from siblings like credit_balance and list_inbox_events by focusing on the credit ledger. However, it lacks an explicit action verb such as 'list' or 'retrieve', which slightly reduces clarity.

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 implies usage by naming the event types and endpoint, but does not explicitly state when to use this tool versus alternatives like list_inbox_events or credit_balance. No exclusions or sibling comparisons are provided, leaving the agent to infer the right context.

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