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

readOnlyHint=true already establishes this as a safe read. The description adds genuinely useful behavior beyond the annotation: newest-first default ordering, the default exclusion of cancelled registrations, and the note that the 'extended' view is slow and large. It does not cover pagination limits or rate limiting, keeping it out of 5 territory.

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?

Three sentences, front-loaded with purpose and return payload before filters and the REST endpoint hint. Dense but every clause carries information; the trailing 'Tito: GET /:account/:event/registrations.' is minor filler but the rest earns its place.

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 12 parameters, no output schema, and a read-only annotation, the description does well by enumerating returned fields and disclosing default ordering and the cancelled-exclusion rule. It leaves pagination defaults and the full response shape to the schema, which is acceptable given there is no output schema, but a short note on paging would make it fully complete.

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%, so every parameter already has a description covering enums, formats, and Tito query mapping. The description echoes the filter semantics (free-text fields, state filtering) but adds no syntax or constraint information the schema lacks, so 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 (list an event's registrations — Tito's orders) and enumerates what is returned (buyer name/email, reference, total, state, flags, discount code, ticket quantities), plus ordering. An agent can distinguish it from tito_get_registration (single record) and the other tito_list_* siblings 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?

Explains the filtering dimensions (free text, state, created/updated time) and the key default behavior that cancelled registrations are excluded unless 'cancelled' is in states. It does not explicitly name alternatives such as tito_get_registration or tito_list_refunds, so it stops short of full when/when-not routing.

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