fetch_balance

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

With no annotations, the description carries the full behavioral burden and does so well: it discloses the auth requirement, that several fields are derived from mirrored state and may be null with a companion <field>_error, that null means UNKNOWN not zero, that leverage is always null, and that funding_paid is always present and paid-positive. This is unusually rich semantic disclosure that goes well beyond field naming.

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?

Purpose is front-loaded in the first clause, followed by progressively finer caveats about null handling and sign conventions. Dense but each sentence carries non-obvious information; the funding_paid contrast may reiterate a point, keeping it just short of fully tight.

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?

With no annotations and no output schema, the description must explain the tricky return fields, and it covers the highest-risk ones (null semantics, leverage always null, funding_paid sign). It does not describe the overall shape of 'positions' or equity composition, and offers no routing against sibling snapshots, leaving a small gap.

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 per the rules the baseline is 4 and there is nothing for the description to clarify. The description's detailed semantics instead cover the return fields, which is appropriate given the absence of both a schema and an output schema.

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+resource: 'Get the authenticated account snapshot: collateral balance, equity, and positions.' An agent immediately knows this is a read of account state. However, it never distinguishes itself from the many overlapping siblings (fetch_account_summary, fetch_account_state, get_balance, fetch_positions, get_account_state), so the agent cannot tell which near-duplicate to pick.

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 only usage signal is 'Requires API credentials.' There is no when-to-use vs when-not guidance, no mention of alternatives like fetch_account_state or fetch_positions, and no scenario that selects this tool over its many lookalike siblings.

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