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

With no annotations, the description carries the full burden and does reasonably well: it discloses that the call is free (no unit cost), its authentication requirement via _meta[satledger/api-key], and what it returns. It omits rate limits or whether the cost table is exhaustive, but covers the two behaviors an agent most needs.

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, front-loaded with the return value, then the cost rationale, then auth. No filler and nothing buried.

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?

There is no output schema, so the description correctly takes on the job of explaining what comes back (units remaining and per-operation costs) and how to authenticate. Adequate for a single-optional-parameter read tool, with only minor behavioral gaps.

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 100%, so the api_key parameter and its _meta preference are already documented in the schema. The description's mention of _meta[satledger/api-key] reinforces the same information rather than adding new semantics, so the baseline 3 applies.

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 precisely what the tool returns: remaining units plus the cost of each operation, which is more specific than the title 'Workspace balance'. It implies a read-only balance check, distinguishable from mutation siblings like top_up_workspace or record_usage, though it never names those siblings explicitly.

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?

'Free, so you can plan before you are refused' gives a clear operating context: call this before spending operations to avoid budget refusal. It stops short of naming alternatives (e.g., top_up_workspace for adding credit), so it is clear context without explicit routing.

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