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

Goes well beyond the annotations by disclosing cost against account balance, irreversibility ('cannot be recalled'), TCPA/CTIA compliance enforcement and sender liability, the aggregate 100-recipient cap, and per-contact placeholder substitution. These are consequences an agent cannot infer from destructiveHint/idempotentHint alone.

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?

Everything critical is front-loaded in the first clause (write, real messages, cost, irreversible); no filler sentences, and the trailing POST path is a compact scoping detail. Reasonably dense but each sentence carries a distinct constraint.

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 destructive mutation with no output schema, the description covers cost, reversibility, consent, confirmation, and recipient limits. It does not say what comes back (message ids/status) or how partial failures behave, which would help an agent verify a send.

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 100%, so baseline 3 applies, but the description adds two things the schema does not: the 100 cap is a total across all recipient arrays (schema caps each at 100 individually), and {{firstName}}-style placeholders are resolved per contact. Recipient identifier types are restated rather than newly explained.

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 ('SEND REAL TEXT MESSAGES') and resource, and the 'WRITE:' prefix immediately distinguishes it from the read-oriented siblings (get_message, list_messages). The endpoint and channel types (SMS/MMS via media) make the scope unambiguous.

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 about when-and-how: only text opted-in people, confirm recipients and text with the user first, and the recipient identifier options are enumerated. It lacks a named alternative ('to draft or preview, use X') but the conditions for correct use are clear.

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