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

No annotations exist, so the description bears the full burden. It does add value by disclosing that line items and derived totals come back, but says nothing about permissions, error behavior for a missing id, or whether totals are computed server-side at read time.

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?

One sentence, zero waste, and the key information (single invoice, by id, returns line items and totals) is front-loaded.

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 single-parameter read with a complete schema, the description covers what it returns well enough that an agent can call it confidently. The absence of any output schema makes the brief return-value note valuable, though error and permission context is still missing.

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% for the single 'id' parameter, so the schema already does the documentation work. The description adds only 'by id' with no format, prefix, or example, which is the expected baseline when the schema is complete.

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?

Specific verb ('Fetch') plus resource ('one invoice') and scope ('by id'), with a note that line items and derived totals are included. It is distinguishable from invoiceflow_list_invoices by the singular/id-based framing, though it never names that sibling.

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?

Usage is only implied: the singular 'by id' framing signals retrieval of one known invoice rather than a listing. There is no explicit when-to-use statement and no pointer to invoiceflow_list_invoices as the alternative for discovery.

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