start_qr_login

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

Annotations already declare readOnlyHint and openWorldHint, so safety is partly covered, but the description adds genuinely useful side-effect context: no local credentials are persisted and the write happens in a separate tool. It does not mention QR expiry/refresh behavior, which would be the remaining gap.

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 short sentences, front-loaded with the return value and followed by the credential-handling note. No filler, though the redundant English '(QR code login)' parenthetical adds little.

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?

With no input parameters and no output schema, the description adequately covers what the tool produces (an inline QR image) and how it relates to the completion step. Only the lifecycle details of the QR code (expiry, polling cadence) are absent, which is a minor gap.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline of 4 applies. Schema coverage is 100% and trivially 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?

States a specific action and return artifact ('returns an inline QR code image') and explicitly distinguishes itself from the sibling that performs the write ('credentials are written by complete_qr_login'). An agent can select it without opening the schema.

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 description makes the pairing with complete_qr_login clear, implying this is the entry step of a two-call flow. It does not state explicit preconditions (e.g., whether an existing session blocks the call) or an explicit 'when not to use', so it stops short of a 5.

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