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

Annotations only declare readOnlyHint=false; the description adds real value beyond that: 'WRITES: this call changes stored state and is not safe to repeat blindly' discloses a mutation and non-idempotency warning, plus source-type restrictions and the signing requirement. This is meaningful behavioral context the annotations do not carry.

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?

Front-loads the core action, then layers constraints and the write warning. Sentences are long and jargon-heavy but each conveys distinct information (source restriction, signature requirement, declaration semantics, mutation warning), so little is wasted.

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 7-param write tool with no output schema, the description covers the essential behaviors: what is recorded, source eligibility, signing requirements, declaration semantics, and the state-changing warning. Only the undocumented scalar params (secret, tx_hash, binding_id) are left to the schema.

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 coverage is 57%, so baseline is 3. The description clarifies funding_relationship as a 'controlled declaration' the chain cannot prove, adding semantic nuance, but leaves secret, tx_hash, and binding_id undocumented in both description and 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 and resource: 'join a binding to an exact finalized Base Transfer of the binding's own asset (USDC or 1F916)'. An agent can distinguish this from siblings like payout_binding or payouts, though the phrasing is dense and domain-specific.

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?

Explicit when-not guidance: only EOA Transfer sources producing an EIP-191 signature are accepted, while Safe/ERC-4337/custodial/contract-wallet sources cannot be recorded, with ERC-1271 named as a follow-up. Also scopes the call to a 'payment fact only, never a docket-delivery verdict'. No named alternative tool, but the constraints are clear.

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