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

Annotations already declare readOnly, idempotent, and non-open-world, so safety is covered. The description adds useful behavior beyond that: it is a fixed snapshot (snapshot_date) rather than live counts, and it returns a bounded set (only 3 spec changes). It does not state freshness/caching policy or whether results can lag, which matters for a snapshot-style tool.

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?

Front-loaded with the returned fields and kept short, with the inline example earning its place because no output schema exists. The example is truncated relative to the promised payload (no 30-day count, no spec changes shown), which is a small source of ambiguity rather than padding.

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?

No input parameters and no output schema, so the description must carry the return shape itself — and it does, via an enumerated field list plus a sample payload and a snapshot-date caveat. An agent has everything needed to decide to call it and to interpret the response.

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?

Zero parameters, so there is nothing to explain; the description explicitly confirms "No arguments", removing any doubt about required input. Baseline for a 0-param tool.

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 enumerates exactly what is returned: total servers, new servers over 7/30 days, 3 latest MCP and A2A spec changes with links, and snapshot date. It reads as the union of the sibling tools (registry_totals, daily_new_counts, spec_changes_since, snapshot_info) but never names them, so the differentiation is implicit rather than explicit.

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?

Includes a concrete usage trigger ("Good for 'How big is the MCP ecosystem and what changed lately?'") and notes "No arguments", which is clear context for when to reach for it. It stops short of telling the agent when NOT to use it or that calling this is preferable to chaining the narrower siblings.

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