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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds useful data-minimization context ('No other account details or API keys are returned'), but the fragment 'Zero credits.' is ambiguous — it could mean the call costs nothing, the balance is zero, or credits are not the return type — which undercuts clarity rather than adding to it.

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 short and front-loads the core action, which is good. However, the two-word fragment 'Zero credits.' is structural noise whose meaning an agent cannot reliably resolve, so not every sentence clearly earns its place.

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 zero-parameter read with complete annotations, the description covers who the data belongs to and what is not returned. With no output schema, it could say more about the return shape (a scalar balance versus an object), but the gap is minor for this complexity level.

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 tool takes no parameters, so there is nothing for the description to disambiguate; the empty schema with additionalProperties=false is self-explanatory. Baseline 4 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?

States a specific verb ('Read') and resource ('the authenticated account's current database balance'), scoped to the caller's own account. It stops short of naming a sibling, though the clause 'No other account details' implicitly separates it from signalshelf_profile.

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?

Usage is only implied: an agent can infer this is the balance lookup, and the exclusion of account details hints that signalshelf_profile covers the rest. There is no explicit when-to-use or when-not-to-use statement, and no sibling is named.

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