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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is known. The description adds genuine value beyond that by disclosing the tool's evidential limits — it returns domain configuration only, not live DNS/TLS/HTTP state — which prevents an agent from over-trusting the output. It does not mention auth requirements or what happens when a service is omitted.

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 sentences with zero filler, and the core capability is front-loaded ahead of the negative-scope caveat. Every clause contributes either purpose or routing information.

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?

An output schema exists, so return-value shape needn't be explained, and the read-only safety profile is covered by annotations. However, for a 4-parameter tool with two required parameters and sparse schema documentation, the description leaves the scoping semantics (project/environment/service interaction) and auth preconditions unaddressed.

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?

Only 25% of parameters are documented in the schema (context_id), leaving project, environment, and service without descriptions in either location. The description only hints that the listing is scoped "for services," with no clarification of project/environment scoping, requiredness, or what happens when service is omitted. It does not compensate for the low schema 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?

The description uses a specific verb and resource ("List Railway and custom domains for services"), clearly distinguishing this inventory tool from verification tools. It does not explicitly distinguish itself from close Railway siblings like railway_services_list, but the resource scope is unmistakable.

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?

It explicitly states a negative scope ("Does not verify DNS/TLS/HTTP") and names the alternative tools to use for that purpose (dns_lookup, http_check, cert_status), which gives an agent a clear routing decision. It stops short of saying when to choose this over other Railway listing tools such as railway_services_list or railway_environments_list.

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