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

With no annotations provided, the description carries the transparency burden. It discloses that the extension is calculated from the chord root, how the chord is found (root = lowest note), and includes return values. However, it omits error/failure behavior and whether the operation is reversible, leaving some uncertainty for a mutating operation.

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 long but well-structured: a summary, detailed extension list with musical rationales, parameter specs, return statement, and a concrete example. Each section adds value, and the content is front-loaded with the core purpose. Slight verbosity in the extension list is justified by its usefulness.

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?

The description fully addresses the musical logic and returns, and includes an example call. However, it misses explanation of the three locator parameters (unit/track/region indices) and does not cover failure conditions or how the user obtains these indices. Given the tool's complexity and absent annotations, this is a notable 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?

Schema coverage is 0%, so the description must fully explain parameters. It does well for extension, chord_position, octave, and velocity, but completely omits unit_index, track_index, and region_index — three required parameters. These are essential for targeting the chord, and the schema only lists them as titles with no additional meaning.

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 opening sentence 'Add a tension/extension note to an existing chord — jazz harmony' clearly identifies the action and target resource. It further explains the purpose ('This is how triads become jazz chords') and is distinct from sibling tools like add_suspension or add_passing_tones.

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?

Provides clear usage context with per-extension guidance on musical character and appropriate scenarios ('The most common jazz extension', 'Can clash with 3rd — use carefully'). It does not explicitly name alternatives or state when not to use, but the contextual guidance is strong enough.

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