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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is covered. The description adds meaningful context about the tool's informational scope, including which tools render MCP Apps and how behavior differs across clients. It does not discuss response format or limitations, but for a read-only informational tool this is largely sufficient.

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 with zero waste. The first front-loads the full scope of the tool, and the second immediately states suitable use cases. Every clause earns its place and the structure is easy to scan.

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?

Given no parameters, no output schema, and annotations already covering the safety profile, the description provides enough context for correct invocation. It could mention the format of the explanation (e.g., a text summary), but nothing essential for calling the tool is missing.

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?

There are zero parameters, so the baseline is 4. The empty schema requires no additional parameter explanation, and the description appropriately focuses on what the tool explains rather than surface-level argument details.

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 verb ('Explains') and resource ('what the FXMacroData MCP server can do') and enumerates the exact subtopics covered: MCP Apps rendering, plain rows, public vs subscriber access, and cross-client tool selection. It clearly separates this meta-capabilities tool from data-oriented siblings, though it does not explicitly name a sibling such as mcp_auth_guide.

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 explicit contexts for use: questions about what is available, why visuals are not showing, or how to get the same result in a different interface. No exclusions or named alternatives are provided, but the conditions are clear enough for an agent to route correctly.

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