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

With no annotations, the description carries the full behavioral burden and does so well: it discloses that the default is a free unsent draft, that draft=false sends immediately, which fields become required, that sending costs one credit, and that mcp:submit permission is needed.

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 is front-loaded with the core create action and default draft behavior, then moves efficiently through the workflow and send conditions. It is compact without omitting critical context.

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 9-parameter mutation tool with no annotations and no output schema, the description is largely complete: it covers creation, draft versus send, required fields, cost, permission, and workflow. A minor gap is that it only names review_url without fully describing the response shape.

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 78%, so many parameter meanings are already documented. The description adds important cross-field semantics: all fields are optional for a draft, while sending requires all fields except signature, signature_id, and mistake.

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 verb and resource: create a postcard for the authenticated user. It also distinguishes creation from previewing, updating, and submitting via sibling tool names, so an agent can tell what this tool is for without opening other schemas.

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 describes the default draft workflow and the alternatives: preview with preview-postcard-tool, change with update-draft-tool, review at review_url, or send with submit-postcard-tool. It also states when to set draft=false for immediate sending.

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