sap_login

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

Without annotations, the description carries the full burden and does well: it discloses side effects (logs in), prerequisite behavior (must be called first), and return value ('Returns the welcome screen text on success'). It falls slightly short by not describing failure modes or authentication error handling, otherwise this would be a 5.

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?

Three sentences, each with a distinct purpose: core action + prerequisite, ordering constraint, and return value. Zero wasted words; everything earns its place. This is a model of concise, front-loaded technical writing.

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 tool with moderate complexity, this covers all critical aspects: purpose, prerequisite, ordering, and return value. It could add failure/error details, but given the tool's simplicity and the absence of an output schema, this is more than sufficient for an agent to use it correctly.

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 100%, placing us at the baseline of 3. However, the description goes beyond by explaining that the username and password default to environment variables (SAP_USERNAME/SAP_PASSWORD), which isn't just a repeat—it's the key to understanding why the parameters are optional. This adds genuine semantic value beyond the schema.

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 ('Log in to the SAP system via WebGUI'), instantly distinguishing it from the sibling tools, which all start with different actions (navigate, browse, run, etc.). It clearly states the tool handles authentication and provides a success condition, leaving no ambiguity about its purpose.

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 phrase 'Must be called before using any other SAP tool' provides an explicit when-to-use directive and establishes a hard ordering requirement. While it doesn't name alternatives, the sibling list makes it obvious no other tool handles login, making this guidance highly effective.

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