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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description still adds meaningful provenance context beyond that: it discloses that the counts come only from index entries and directly observed MCP checks, and explicitly that uptime/quality/correctness are NOT inferred, which prevents over-reading the output.

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 tight sentences, front-loaded with what is returned and followed by the key limitation. Nothing is redundant and no sentence could be dropped without losing 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?

With no input parameters, no output schema and rich annotations, the description carries most of what an agent needs: what the counts represent and an explicit non-inference caveat. It could go slightly further by hinting at the shape or granularity of the returned counts, which is the only remaining gap.

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 are no parameter semantics to explain; the empty schema with additionalProperties=false is self-explanatory. Baseline for a zero-parameter tool 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?

The description opens with a concrete verb and resource: 'Return aggregate counts of index entries and directly observed MCP checks.' That tells an agent this is an aggregate/status read rather than a per-server lookup like the sibling get_mcp_server_metadata, though it never names a sibling or explicitly contrasts with one.

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?

Usage is only implied: an agent can infer this is the tool for network-level counts, and the second sentence warns what it must not be used to derive (uptime, quality, provider correctness). There is no explicit 'use this when...' or 'use X instead' routing guidance.

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