Log Expense

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

The description adds meaningful operational context beyond the annotations: each call costs $0.10 and requires an API key. The 'Create' action also correctly implies a write operation consistent with readOnlyHint=false. It does not fully describe side effects, but the annotations already cover the basic safety profile.

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 extremely concise: two sentences that deliver purpose, scope, the key alternative, and cost/authentication. No filler or redundant restatement of the schema exists.

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?

The description covers the critical selection criterion, cost, and auth, and an output schema exists so return values need not be explained. However, with nine parameters and low schema coverage, the lack of guidance on how to populate amount, category, currency, and notes leaves some ambiguity for correct invocation.

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 only 33%, and the description does not compensate by explaining amount, date, category, currency, or notes. The only parameter-related value is the direction/income distinction, which is more about tool selection than parameter semantics. Most parameters remain underdocumented.

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 uses a specific verb and resource: 'Create an outgoing expense only.' It clearly differentiates the tool from log_transaction, which handles incoming money. The scope is precise and immediately understandable.

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?

It explicitly states when to use this tool versus the main alternative: for money received via Venmo/Cash App/PayPal/Zelle, use log_transaction with direction=from and type=income. This gives the agent an unambiguous routing decision.

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