Get a song: its status, title, cover, lyrics and a short-lived audio link. Hosts that show MCP Apps draw it as a card with a player and synced lyrics, so there is no need to paste the audio link.
| Name | Required | Description | Default |
|---|---|---|---|
| songId | Yes | Song ID to fetch details for |
| Name | Required | Description | Default |
|---|---|---|---|
| style | Yes | ||
| title | Yes | ||
| lyrics | Yes | ||
| songId | Yes | ||
| status | Yes | ||
| audioUrl | Yes | ||
| duration | Yes | ||
| imageUrl | Yes | ||
| progress | Yes | ||
| createdAt | Yes | ||
| visibility | Yes |
Changes observed during successful MCP inspections.
Output schema / properties / audioUrl / anyOfRemoved value: -[
- {
- "type": "string"
- },
- {
- "type": "null"
- }
-]Output schema / properties / audioUrl / typeAdded value: +[
+ "string",
+ "null"
+]Output schema / properties / duration / anyOfRemoved value: -[
- {
- "type": "number"
- },
- {
- "type": "null"
- }
-]Output schema / properties / duration / typeAdded value: +[
+ "number",
+ "null"
+]Output schema / properties / imageUrl / anyOfRemoved value: -[
- {
- "type": "string"
- },
- {
- "type": "null"
- }
-]Output schema / properties / imageUrl / typeAdded value: +[
+ "string",
+ "null"
+]Output schema / properties / progress / anyOfPrevious value: -[
- {
- "properties": {
- "etaMs": {
- "anyOf": [
- {
- "type": "number"
- },
- {
- "type": "null"
- }
- ]
- },
- "from": {
- "type": "number"
- },
- "label": {
- "type": "string"
- },
- "now": {
- "type": "number"
- },
- "stage": {
- "type": "string"
- },
- "stageExpectedMs": {
- "anyOf": [
- {
- "type": "number"
- },
- {
- "type": "null"
- }
- ]
- },
- "stageStartedAt": {
- "type": "number"
- },
- "to": {
- "type": "number"
- }
- },
- "required": [
- "stage",
- "label",
- "now",
- "stageStartedAt",
- "stageExpectedMs",
- "etaMs",
- "from",
- "to"
- ],
- "type": "object"
- },
- {
- "type": "null"
- }
-]New value: +[
+ {
+ "properties": {
+ "etaMs": {
+ "type": [
+ "number",
+ "null"
+ ]
+ },
+ "from": {
+ "type": "number"
+ },
+ "label": {
+ "type": "string"
+ },
+ "now": {
+ "type": "number"
+ },
+ "stage": {
+ "type": "string"
+ },
+ "stageExpectedMs": {
+ "type": [
+ "number",
+ "null"
+ ]
+ },
+ "stageStartedAt": {
+ "type": "number"
+ },
+ "to": {
+ "type": "number"
+ }
+ },
+ "required": [
+ "stage",
+ "label",
+ "now",
+ "stageStartedAt",
+ "stageExpectedMs",
+ "etaMs",
+ "from",
+ "to"
+ ],
+ "type": "object"
+ },
+ {
+ "type": "null"
+ }
+]Output schema / properties / style / anyOfRemoved value: -[
- {
- "type": "string"
- },
- {
- "type": "null"
- }
-]Output schema / properties / style / typeAdded value: +[
+ "string",
+ "null"
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false. The description adds useful behavioral context beyond annotations: it lists what the response contains, notes the audio link is short-lived, and explains how MCP Apps hosts render the result as a card with a player and synced lyrics.
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 two tight sentences, front-loads the core purpose and returned fields, and then adds the host-rendering detail without repetition or waste.
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 simple read-only retrieval tool with one required parameter, full schema coverage, annotations covering safety, and an output schema already present, the description provides enough context. It explains the returned content and host rendering behavior without needing to restate the output 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 description coverage is 100%, and the sole parameter 'songId' is clearly documented as 'Song ID to fetch details for'. The description does not add any further semantics about the ID format or source, so the schema carries the parameter explanation.
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 description gives a specific verb and resource ('Get a song') and enumerates the returned fields: status, title, cover, lyrics, and a short-lived audio link. It is clearly a detail-fetch tool, but it does not explicitly differentiate itself from siblings such as get_song_parts or get_my_songs.
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 description implies usage by explaining that hosts rendering MCP Apps will show a card with a player and synced lyrics, and that the audio link need not be pasted. However, it gives no explicit guidance on when to choose this tool over alternatives like get_song_parts or get_my_songs.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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