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

Annotations already declare readOnlyHint, idempotentHint, and closed-world behavior, so the safety profile is covered. The description adds useful behavioral context: the default 30-day window and the example return shape {since, count, by_namespace_type}.

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 description is front-loaded and appropriately short. The output example and default behavior are useful, though the date format is repeated from the schema and could be trimmed.

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 simple read-only count tool with one optional parameter and no output schema, the description supplies the default window and example return fields. It does not define namespace type values, but that is reasonably delegated to the namespace_types sibling.

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 the single date parameter is already fully documented, including format and default behavior. The description repeats the YYYY-MM-DD format and gives an example call, but adds little semantic meaning beyond the schema.

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 states a specific resource and scope: MCP servers first published on or after a given date, split by namespace type. It is clear enough to distinguish from aggregate siblings like registry_totals, but it does not explicitly name daily_new_counts as the daily-breakdown alternative.

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 gives a clear usage example ('How many new MCP servers since October?') and explains the no-argument default of counting the last 30 days. It does not provide exclusions or explicitly route agents to a sibling tool.

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