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

With no annotations, the description carries the full behavioral disclosure burden. It adds useful context beyond the name: data is 'in-memory' (not persisted), the tool is an 'MVP' (likely early-stage), and it is 'Free' (no billing impact). It does not explicitly say it is read-only, but 'Show' strongly implies no mutation.

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 extremely concise, with the main action front-loaded and only two short clauses. Every word adds value: 'in-memory' clarifies behavior, 'for this isolate' defines scope, 'MVP' sets expectations, and 'Free' is a key operational trait.

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 one-optional-parameter tool, the description covers the core purpose and a few behavioral caveats. However, there is no output schema and the description does not describe what the response will contain (e.g., values, units, format), and 'this isolate' is not fully explained.

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 single parameter tenantId is fully described in the input schema with its optionality and default value, so schema coverage is 100%. The tool description does not add extra meaning about this parameter, but the baseline of 3 applies because the schema already documents it adequately.

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 clearly states the tool's function with a specific verb ('Show') and resource ('in-memory spend / rate usage for this isolate'), and the 'Free' note adds a distinguishing characteristic. It is easily differentiated from the unrelated sibling tools, none of which concern spend or rate monitoring.

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?

The description implies when to use this tool: when you need to check current spend or rate usage, and the 'Free' note suggests it is safe/cost-free to call. However, it does not explicitly state when not to use it or mention any alternative tools, though the siblings appear unrelated.

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