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

readOnlyHint=true already establishes the safe-read profile, so the annotation carries the main behavioral burden. The description adds useful content-level context (that line items, taxes and totals are returned) and the underlying REST endpoint, but says nothing about permissions or error behavior.

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 compact sentences, front-loaded with the core purpose and followed by the endpoint. No filler or redundancy; every clause earns its place.

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?

There is no output schema, so the description carries the return-value burden and does so at a summary level (line items, taxes, totals). For a simple single-entity read with full param coverage, that is nearly complete, though it omits nested detail and error semantics.

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% (the single invoice_id is documented in the schema), so baseline is 3. The 'GET /invoices/{id}' text maps the parameter to a path variable but adds no format or constraint detail beyond what anyOf/pattern already provide.

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 states a clear verb ('Retrieve') and resource ('one invoice') and enumerates what comes back (line items, taxes, totals). It implicitly contrasts with teachworks_list_invoices by specifying a single invoice, but never names the sibling explicitly.

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: 'one invoice' and the /invoices/{id} path suggest this is the single-record fetch versus the list tool, but there is no explicit when-to-use or when-not-to-use guidance and no alternative is named.

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