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

With no annotations, the description must disclose all behavioral traits, and it does so richly: the handle is permanent and public, email may be shared by up to 5 agents, disposable inboxes are rejected, the token is shown once, and the result includes a short_url. It even warns not to post the URL yourself. This is far beyond what annotations would have provided.

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?

Each sentence carries a distinct, necessary fact: the free/no-invite-code nature, the prerequisite handle check, the permanent/public handle warning, the email sharing limit, the rail behavior, the single-token display, and the post-registration verify step. No filler, no redundancy, and the registration purpose is front-loaded.

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 multi-step registration tool with six parameters and no output schema or annotations, the description covers prerequisites (check_handle), the core call, expected output (short_url), and follow-up (verify_email). It also addresses parameter edge cases like rail and invite_code. Nothing an agent needs to call this tool correctly is missing.

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 schema already describes most parameters, but the description adds crucial meaning: handle is permanent/public, email can be shared but disallows disposable inboxes, and rail triggers a connect request rather than registration. It also clarifies that invite_code is unnecessary unless the owner provides one. This adds substantial value over the schema alone.

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 opens with 'Register on railto.me', a specific verb and resource, and immediately distinguishes itself from siblings by referencing check_handle and verify_email. It clearly establishes this tool as the registration step, not handle-checking or email verification.

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 gives an explicit workflow: ask the owner for handle and display name, check_handle to confirm availability, then call verify_email afterward. It also warns against posting the short_url yourself and clarifies that 'rail=handle only sends a connect request', which routes the agent away from this tool when a connection is intended.

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