sub-agent costs (Token Meter)

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

Annotations already declare readOnlyHint=true, destructiveHint=false, and idempotentHint=true, so the tool is safe and idempotent. The description adds behavioral context by explaining the split and pairing with latency, and notes the need for prior data refresh. No contradictions with annotations.

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 three sentences and front-loads the primary function. It is clear and to the point, though the second sentence could be slightly more concise. Still, it earns its place without unnecessary verbosity.

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 the tool has three optional parameters and no output schema, the description adequately conveys what the tool returns (split spend, list of priciest sub-agents, latency pairing) and the prerequisite action. It is complete enough for an agent to invoke correctly.

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 description coverage is only 33% (scope has a description). The tool description does not elaborate on the three parameters (limit, scope, period), leaving the agent to rely solely on schema defaults and enum options. This is insufficient given low coverage.

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 splits spend into main-session vs sub-agent work, lists priciest sub-agents, and pairs with latency. It answers a specific question ('are my sub-agents worth what they cost') and distinguishes itself from sibling tools like usage_summary or recent_sessions by focusing on sub-agent cost analysis.

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 advises running `refresh_data` or `ingest --force` to ensure older rows are tagged, providing a clear prerequisite. It also frames the tool's purpose as answering a specific cost-value question. However, it does not explicitly mention when to avoid this tool or suggest alternatives among siblings.

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