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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is fully covered by structured data. The description adds the useful context that this returns metadata (counts, date ranges, venues, licensing) rather than launch records, but says nothing about response shape, size, or freshness beyond the annotations. Adds some value, but modest against an already-covered annotation set.

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, both load-bearing: the first defines the payload, the second defines the call condition. The content categories are front-loaded with no filler or restatement of the title.

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?

There is no output schema, so the description carries the burden of describing returns, and it does so by enumerating the coverage dimensions an agent will receive. It stops short of describing format or granularity, but for a parameterless read-only metadata call this is close to 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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; the schema coverage signal of 100% on an empty object is consistent with that. A 0-parameter tool sits at the baseline of 4 by the stated rule.

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 names the resource (the register's coverage figures) and enumerates exactly what those figures contain: launch counts, start date, venues, and free-vs-licensed breakdown. It is clearly distinct from the sibling lookup_launch and search_ticker_or_name tools, which retrieve launches rather than register metadata. It is a noun-phrase description rather than an explicit verb+resource, which keeps it just short of a 5.

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?

"Use this to state the basis of any answer drawn from the register" gives a concrete when-to-use trigger tied to grounding answers in provenance. It does not explicitly name alternatives or state when-not to use it, so it falls short of full routing guidance.

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