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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds genuine context beyond that: it discloses the shape of the returned data and, notably, that it reports whether a part's words can be changed — a mutability signal an agent needs before editing. It says nothing about pagination or failure behavior, which keeps it short of a 5.

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?

Two dense sentences with no filler. The resource and return shape come first, and the sequencing instruction to run it before change_lyrics is placed at the end as the actionable takeaway. Every clause 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 single-parameter read tool with no output schema and coverage from annotations, this is fully sufficient: it describes what is returned, the identifier format of parts, the editability flag, and the workflow context. An agent has everything needed to select and invoke it correctly.

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 description coverage is 100% and the single songId parameter is already documented in the schema, including where to obtain the id (get_my_songs or a song card). The description only refers obliquely to 'one of their songs' and adds no new syntax or constraint, so baseline 3 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 precise verb and resource ('List the parts of one of their songs') and goes further to enumerate the returned content: part ids like verse#1/chorus#2, the lines sung in each, their times, and whether the words are editable. That level of specificity lets an agent distinguish this from generic song-fetching siblings without opening the schema.

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?

Explicitly prescribes the sequencing: 'Call it before change_lyrics to find the part they mean,' which tells the agent exactly when this tool is the right step. It stops short of any when-not guidance or differentiation from the overlapping sibling get_song_details, so it is clear context rather than a full decision rule.

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