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

Goes well beyond the annotations: it discloses that MCP registrations are OWNERLESS (owner_id:null, claimed:false), that the result returns a claim recipe, and that omitting url degrades to long-poll. The closing REST-API User-Agent note is tangential to an MCP transport and risks confusing an agent, and the non-idempotent behavior for duplicate agent_id is never addressed, keeping it below 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?

The core action is front-loaded, but the tunnel one-liner and the 'there is NO /one-liner endpoint' warning are repeated across the description and the url schema field, and the Cloudflare 1010 UA note is a defensive aside for a different transport. Content is useful but the prose is over-sized with duplicated warnings.

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 11 parameters, one required, no output schema, and creation semantics, the description covers the two riskiest areas: delivery setup (url vs long-poll) and post-registration ownership/claim. It even sketches the return (a claim recipe). What remains thin is identity conflict handling for a non-idempotent registration with a caller-supplied agent_id.

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%, so every parameter is already documented in the input schema, including the url/tunnel guidance and the type enum. The description largely restates the url semantics rather than adding new parameter-level meaning, so the baseline 3 applies.

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 ('Register this agent in the directory') plus the purpose ('so other agents can discover it'), which cleanly distinguishes it from siblings like get_agent, list_agents, and update_profile. An agent can identify the tool's job 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?

Gives strong operational guidance: ALWAYS supply the saved webhook at registration/come-online time, and omit url only when no endpoint can be exposed (then long-poll). It does not name sibling alternatives or spell out re-registration/duplicate-id behavior, so it stops short of a 5, but usage conditions are explicit rather than implied.

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