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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuine behavioral content: guide switches the tool into returning a playbook's steps, and store is required to resolve chart names. It does not say what a no-argument call returns, how response_format changes output, or what the guide steps look like.

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?

Three short sentences, no filler, with the trigger and the exclusion both stated up front. The enum semantics are packed into a compact clause rather than a bulleted restatement of the schema.

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 zero required parameters and no output schema, the agent needs to know what a bare call returns and how the modes differ, and the description only answers half of that. It also leaves the boundary against charts_get ambiguous by advertising "charts" in its own scope while telling the agent to go elsewhere for rankings.

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 coverage is only 25% (just context), so the description must carry the load, and it does for the two ambiguous parameters: it explains that store maps to chart names and spells out what each guide enum value means, which the schema does not. It leaves response_format totally unexplained and says nothing about default behavior when no parameters are sent.

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 never states a crisp verb+resource; it enumerates a grab-bag of things ("stores, app counts, countries, freshness, charts or metrics") and then pivots to a guide playbook, so the tool reads as several tools in one. It does name one sibling exclusion, but the overlap with charts_get is muddled by listing "charts" as something this tool provides.

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 both a when-to-use trigger and an explicit when-not ("Do not use for rankings; use charts_get"), and it explains the three guide modes with concrete scenarios (a store's week, compare apps, an MCP server's tools). The guidance is weakened by the vague catch-all opening clause, which could be read as an invitation to use this for almost anything.

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