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

Annotations declare readOnlyHint=true and destructiveHint=false, and the description reinforces this with 'public and read-only, no token needed' and 'This tool changes nothing'. It adds substantial context beyond the annotations: pricing model (6%/3%), return document location (identical to /.well-known/comos-vendor.json), and next-step application flow. No contradiction.

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?

The description runs long for a zero-required-param read tool. Pricing details and OAuth walkthrough could arguably live in federation_apply's documentation, and the 'door's window' metaphor appears twice (title and body). However, each clause does convey information, and the return-shape spec at the end is valuable. It's dense but not bloated — a long paragraph where a few sentences would have sufficed.

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 read-only tool with strong annotations and no output schema, the description is thorough: it discloses the return shape inline ({ offer, how_to_apply }), documents auth requirements (none), notes idempotency, and describes the operational flow. There are no unexplained side effects or missing behavioral surfaces that annotations don't already cover.

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 only parameter (channel) is already fully documented in the input schema. The description adds minimal parametric value beyond the example invocation 'call federation_offer with arguments {}', which is a slightly useful illustration but trivial given zero required parameters. Meets the baseline-3 for high coverage.

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?

Uses a specific verb+resource ('Read the ComOS network's vendor offer') plus scoping constraints ('public and read-only, no token needed'). The title 'The Door's Window' and the explicit contrast with federation_apply ('this tool changes nothing... federation_apply is the door') sharply distinguish it from siblings like federation_apply.

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?

Explicitly names the alternative tool (federation_apply), describes the full workflow ('obtain an OAuth token... then call federation_apply with it'), and states when no auth is needed. The 'no token needed' line tells agents not to chain an auth step for this particular call — a clear when-to-use signal.

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