fetch_invoice_emails

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

Describes core behavior (fetch, extract, store) and mentions 'configured IMAP mailbox,' but omits details like whether emails are marked as read, authentication requirements, rate limits, or empty mailbox handling. With no annotations, more transparency about side effects and preconditions would be beneficial.

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 concise sentences plus a bulleted list of examples. Front-loaded with the primary purpose, followed by motivation and illustrative queries. No unnecessary words.

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?

Covers purpose, motivation, and examples well for a zero-parameter tool without output schema. However, lacks mention of any return value or confirmation after storing cost entries, which could be helpful for agent coordination.

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?

No parameters exist in the input schema, so baseline score of 4 applies. Description does not need to add parameter information, and it correctly focuses on tool behavior.

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?

Description clearly states the tool fetches unread invoice emails, extracts amounts, stores as cost entries, and includes specific examples. It distinguishes itself from sibling audit/cost tools by addressing a specific billing API gap for vendors like PagerDuty, New Relic, and GitHub Enterprise.

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?

Examples illustrate appropriate use cases (e.g., parsing billing inbox, checking vendor charges). While it doesn't explicitly state when not to use, the context of solving a billing API gap implies usage when direct API access is unavailable. Lacks explicit exclusions but provides clear context.

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