Check budget status

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

Annotations already provide readOnlyHint and idempotentHint. Description adds that it's read-only, cannot set budget, and details the source env var BUDGET_SATS and immutability during runtime. This adds valuable context beyond 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?

Description is four sentences, front-loaded with main purpose. Each sentence adds value: purpose, when-to-use, limitation, and sibling reference. No wasted words.

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, clear annotations, and explicit description of what it returns and limitations, the tool is well-described for an agent. Lacks output format but it's a simple read-only query; still complete enough.

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?

Input schema has no parameters, so schema description coverage is 100% vacuously. Baseline for 0 parameters is 4. Description does not need to add parameter info.

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 'returns the session budget cap configured at startup', uses specific verb 'Returns' and resource 'session budget cap'. It distinguishes from sibling l402_balance which tracks remaining balance.

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?

Explicitly says when to use: 'useful at the start of a session before making any API calls'. It also says what not to use for: 'CANNOT set or change the budget', and provides alternative (restart server). Distinguishes from l402_balance for remaining balance.

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